Add C23 enum types and packing attributes support for C parser

[axd1x8a]

Add Support for C23 Enum Types and Refine Sizing

Key changes:

• C23 Underlying Type Parsing: The parser now correctly handles enum : <type> syntax.
• Enum Resizing:
  • For enums with an explicit C23 underlying type, the size is determined by that type (validated to be 1, 2, 4, or 8 bytes), or the minimum size required by its members, whichever is larger
  • For enums without an explicit type, the size is now set to the minimum length required by their members, like it done by compilers
    Enums with __attribute__((__packed__)) or [[packed]] attributes and without an explicit type will be resized to fit largest member.

FIxes:

• CParser treats all enums as size 4 #4518

[axd1x8a]

Oh, I just read the comments in the original issue, maybe automatic resizing should be removed?

[axd1x8a]

I've added handling for __attribute__((__packed__)) and [[packed]] attributes (supported by GCC/Clang) for more explicit enum sizing, instead of always resizing. I also added tests for negative values in these enums, as I saw some issues for this.

Could you please link any relevant issues? I think there are more of them than I found.

[antoniovazquezblanco]

The following PR is related to a similar issue.

#6780

Referenced for tracking.

I hope this helps @emteere.

Thanks!

[axd1x8a]

Oh, I was unaware that a separate PR existed for packed attributes.
I hope it won't take as long to merge this as the previous one

[antoniovazquezblanco]

I hope so but things here move slowly...

[Zeranoe]

I missed this when I opened #8539, which adds the type support. It appears we independently arrived at roughly the same code, though I used TypeName() instead of BuiltInTypeSpecifier() because it will properly handle things like enum _PROOF_OF_POSSESSION_FLAGS : DWORD (#8495).

[axd1x8a]

Could someone review any of these PRs? The option to specify the size of an enum is useful when generating C code for Ghidra to parse, but having to build a custom version every time I need to do so is very troublesome