Nearly fully documented the optional PE header.

[JohnScience]

There's still some work needed for documentation of data directories field in the optional header but it's a separate module.

This PR also...

• introduces two new modules for constants that are used in the optional header (dll_characteristic and subsystem).
• further refines the documentation of the COFF header module.

[JohnScience]

@m4b

[m4b]

release: non-breaking

[JohnScience]

to be honest this is quite a lot of documentation to review, though not a bad thing, thank you for the PR! What a strange world we're entering with gen ai though :)

my only major concerns are about the various doc aliases, they appear to alias things that don't exist, and i think that should be fixed before merging

Doc aliases improve the searchability of various items by allowing users finding them by their Windows name. See Rustdoc > Advanced features > Add aliases for an item in documentation search