test: Ensure 8MiB of stack size for key generation

This commit ensures that the call to `StaticKEM::keygen` has a stack of
8MiB.

Especially on Darwin system, this commit is necessary in order to
prevent a stack overflow, as this system only provides stack sizes of
roughly 500KB which is way to small for a Classic McEliece key.

Fixes #118

Cargo.toml

@@ -36,6 +36,7 @@ anyhow = "1.0.71"
 [dev-dependencies]
 criterion = "0.4.0"
 test_bin = "0.4.0"
+stacker = "0.1.15"
 
 [features]
 default = ["log", "env_logger"]