chore: Reorganize memfd secret policy

- Policy is now set in main.rs, not cli.rs.
- Feature is called experiment_memfd_secret, not enable_memfd_alloc

This also fixes the last remaining warnings.

rosenpass/tests/integration_test.rs

@@ -15,9 +15,19 @@ use std::io::Write;
 
 const BIN: &str = "rosenpass";
 
+fn setup_tests() {
+    use rosenpass_secret_memory as SM;
+    #[cfg(feature = "experiment_memfd_secret")]
+    SM::secret_policy_try_use_memfd_secrets();
+    #[cfg(not(feature = "experiment_memfd_secret"))]
+    SM::secret_policy_use_only_malloc_secrets();
+}
+
 // check that we can generate keys
 #[test]
 fn generate_keys() {
+    setup_tests();
+
     let tmpdir = PathBuf::from(env!("CARGO_TARGET_TMPDIR")).join("keygen");
     fs::create_dir_all(&tmpdir).unwrap();
 
@@ -134,6 +144,7 @@ fn run_server_client_exchange(
 #[test]
 #[serial]
 fn check_exchange_under_normal() {
+    setup_tests();
     setup_logging();
 
     let tmpdir = PathBuf::from(env!("CARGO_TARGET_TMPDIR")).join("exchange");
@@ -206,6 +217,7 @@ fn check_exchange_under_normal() {
 #[test]
 #[serial]
 fn check_exchange_under_dos() {
+    setup_tests();
     setup_logging();
 
     //Generate binary with responder with feature integration_test