Safety Audit

[Anders429]

This PR contains the safety audit conducted in #70. It also contains a fix to #75, fixing the trybuild tests. A few other things are thrown in as well; this one really took a while. Current me is cursing past me for not writing SAFETY comments when the code was originally written, especially considering how large and complicated this library has become.

[Anders429]

Looks like that trybuild test is still failing due to some kind of regression in the latest nightly. On that note, something should be done to make that error message better. It should only appear once, not once for every component included in the entities.

[codecov-commenter]

Codecov Report

Merging #77 (cd19907) into master (fb0e3bc) will increase coverage by 18.53%.
The diff coverage is 55.80%.

@@             Coverage Diff             @@
##           master      #77       +/-   ##
===========================================
+ Coverage   21.68%   40.22%   +18.53%     
===========================================
  Files          55       56        +1     
  Lines        4003     5907     +1904     
===========================================
+ Hits          868     2376     +1508     
- Misses       3135     3531      +396     

Impacted Files	Coverage Δ
src/archetype/identifier/impl_serde.rs	0.00% <0.00%> (ø)
src/archetype/impl_debug.rs	0.00% <0.00%> (ø)
src/archetype/impl_eq.rs	0.00% <0.00%> (ø)
src/archetype/impl_serde.rs	0.00% <0.00%> (ø)
src/archetypes/impl_debug.rs	0.00% <0.00%> (ø)
src/archetypes/impl_eq.rs	0.00% <0.00%> (ø)
src/archetypes/iter.rs	0.00% <0.00%> (ø)
src/archetypes/par_iter.rs	0.00% <0.00%> (ø)
src/entities/mod.rs	0.00% <ø> (ø)
src/entities/seal/storage.rs	0.00% <0.00%> (ø)
... and 28 more

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[Anders429]

Turns out, the issue wasn't a regression in nightly at all. In order for rustc to include the path of a standard library function in the error output, the rust-src component needed to be included. This is why I was getting the $RUST/alloc/... path on my local machine, but not on the CI runs.