epee: remove dead code

Each symbol below has no references anywhere in the tree (src/, contrib/,
tests/); the full build still links cleanly. Per-symbol history is given so the
"why is this unused" is auditable (hashes are ancestors of HEAD).

net/connection_basic (all four lost their last caller in the 2022 connection
rewrite, 3be1dbd09 "connection: fix implementation"):
- to_string(t_connection_type): unused free function. Added 9bfa593ee (2015)
  to print a connection's type in a debug log; 3be1dbd09 (2022) switched that
  log line to std::to_string on the enum, orphaning this overload.
- do_send_handler_write / do_send_handler_write_from_queue: trace-only stubs
  added eabb51960 (2015) on the TCP send path; their calls in do_send_chunk /
  the write-completion handler were deleted by 3be1dbd09 (2022). The real send
  path is connection<T>::start_write().
- sleep_before_packet: outbound rate-limit sleep added eabb51960 (2015);
  callers were thinned over time (cf5f62361, 2017) and the last removed by
  3be1dbd09 (2022). Rate-limiting now lives in connection<T>::start_write()
  via the global out-throttle.

net/levin_base:
- struct bucket_head: legacy levin packet header from the 2014 epee import,
  superseded by bucket_head2 (the wire header, `using header = bucket_head2`).
  Its last use went away with the old levin_protocol_handler in 0c545f614
  (2024, "epee/test: remove levin_protocol_handler and core_proxy tests").
- LEVIN_PROTOCOL_VER_0: dead on arrival - present since the 2014 import, never
  referenced (the code uses LEVIN_PROTOCOL_VER_1).

net/net_utils_base (connection-context logging macros):
- LOG_PRINT_CC_L4: levin trace macro (2014 import); all call sites removed in
  5833d66f6 (2017, "Change logging to easylogging++").
- LOG_PRINT_CCONTEXT_L3: had a single "REMOTE PEERLIST" call site, removed in
  the same 5833d66f6 (2017).
- LOG_PRINT_CC_L3: only ever referenced inside LOG_PRINT_CCONTEXT_L3's body,
  never invoked directly - transitively dead once the above was removed.
- LOG_CC: dead on arrival - added in 5833d66f6 (2017) but never invoked.
  (The plain LOG_PRINT_L3 macro that LOG_PRINT_CC_L3/CCONTEXT_L3 wrap is still
  used elsewhere and is left untouched; only these unused CC wrappers go.)

net/network_throttle:
- typedef network_MB: added eabb51960 (2015); its only consumers
  (set_target_kill / m_target_MB) were stripped the same day in 5ce4256e3
  (2015), leaving an unused typedef.

profile_tools:
- START_WAY_POINTS / WAY_POINT / WAY_POINT2: dead on arrival - upstream-epee
  profiling macros present since the 2014 import, never once invoked (they only
  ever appear as definitions in profile_tools.h across all history).
- TIME_MEASURE_PAUSE / TIME_MEASURE_RESTART and their _NS_ variants: dead on
  arrival - added bda8c5983 (2017, "epee: add nanosecond timer and pause/restart
  profiling macros") but never wired to any call site. Of this family only
  TIME_MEASURE_START / TIME_MEASURE_FINISH are actually used.

storages:
- typedef binarybuffer (portable_storage_base): used by the binary store/load
  API since the 2014 import; its last consumer (store_to_binary) was removed in
  7414e2bac (2020, "Change epee binary output from std::stringstream to
  byte_stream").
- the templated min_bytes() member declaration (portable_storage_from_bin):
  declared but never defined or called. Added 7f407c027 (2020-12-26,
  "portable_storage: add some sanity checks on data size") alongside the
  ps_min_bytes<> trait struct, but the size checks were implemented via that
  trait (ps_min_bytes<>::strict), so this member was never defined or wired up
  - dead on arrival. The ps_min_bytes<> trait remains in use and is left intact.

contrib/epee/src/connection_basic.cpp

@@ -67,21 +67,6 @@ namespace
 	}
 }
 
-  std::string to_string(t_connection_type type)
-  {
-	  if (type == e_connection_type_NET)
-		return std::string("NET");
-	  else if (type == e_connection_type_RPC)
-	    return std::string("RPC");
-	  else if (type == e_connection_type_P2P)
-	    return std::string("P2P");
-	  
-	  return std::string("UNKNOWN");
-  }
-
-
-/* ============================================================================ */
-
 class connection_basic_pimpl {
 	public:
 		connection_basic_pimpl(const std::string &name);
@@ -222,46 +207,6 @@ int connection_basic::get_tos_flag() {
 	return connection_basic_pimpl::m_default_tos;
 }
 
-void connection_basic::sleep_before_packet(size_t packet_size, int phase,  int q_len) {
-	double delay=0; // will be calculated
-	do
-	{ // rate limiting
-		if (m_was_shutdown) { 
-			_dbg2("m_was_shutdown - so abort sleep");
-			return;
-		}
-
-		{ 
-			CRITICAL_REGION_LOCAL(	network_throttle_manager::m_lock_get_global_throttle_out );
-			delay = network_throttle_manager::get_global_throttle_out().get_sleep_time_after_tick( packet_size );
-		}
-
-		delay *= 0.50;
-		if (delay > 0) {
-            long int ms = (long int)(delay * 1000);
-			MTRACE("Sleeping in " << __FUNCTION__ << " for " << ms << " ms before packet_size="<<packet_size); // debug sleep
-			boost::this_thread::sleep(boost::posix_time::milliseconds( ms ) );
-		}
-	} while(delay > 0);
-
-// XXX LATER XXX
-	{
-	  CRITICAL_REGION_LOCAL(	network_throttle_manager::m_lock_get_global_throttle_out );
-		network_throttle_manager::get_global_throttle_out().handle_trafic_exact( packet_size ); // increase counter - global
-	}
-
-}
-
-void connection_basic::do_send_handler_write(const void* ptr , size_t cb ) {
-        // No sleeping here; sleeping is done once and for all in connection<t_protocol_handler>::handle_write
-	MTRACE("handler_write (direct) - before ASIO write, for packet="<<cb<<" B (after sleep)");
-}
-
-void connection_basic::do_send_handler_write_from_queue( const boost::system::error_code& e, size_t cb, int q_len ) {
-        // No sleeping here; sleeping is done once and for all in connection<t_protocol_handler>::handle_write
-	MTRACE("handler_write (after write, from queue="<<q_len<<") - before ASIO write, for packet="<<cb<<" B (after sleep)");
-}
-
 void connection_basic::logger_handle_net_read(size_t size) { // network data read
 }