Reenable C4242 and C4244 warnings in libunwind

[AaronRobinsonMSFT]

Fixes #99471
Fixes #100207

Big thanks to @filipnavara for doing this.

Will create upstream (libunwind) patch after confirmation we are clean.

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[AaronRobinsonMSFT]

/cc @janvorli @filipnavara @am11

[am11]

Looks great! :)

Few errors showing up in the CI:

  D:\a\_work\1\s\src\native\external\libunwind\src\aarch64\Gstash_frame.c(57): error C4242: 'function': conversion from 'unw_word_t' to 'long', possible loss of data
  D:\a\_work\1\s\src\native\external\libunwind\src\aarch64\Gstash_frame.c(63): error C4242: 'function': conversion from 'unw_word_t' to 'long', possible loss of data
  D:\a\_work\1\s\src\native\external\libunwind\src\aarch64\Gstash_frame.c(69): error C4242: 'function': conversion from 'unw_word_t' to 'long', possible loss of data
  D:\a\_work\1\s\src\native\external\libunwind\src\aarch64\Gstash_frame.c(75): error C4242: 'function': conversion from 'unw_word_t' to 'long', possible loss of data
  D:\a\_work\1\s\src\native\external\libunwind\src\dwarf\Gexpr.c(369): error C4242: 'function': conversion from 'unw_word_t' to 'int', possible loss of data
  D:\a\_work\1\s\src\native\external\libunwind\src\dwarf\Gparser.c(885): error C4242: '=': conversion from 'unw_word_t' to 'unw_regnum_t', possible loss of data

Will create upstream (libunwind) patch after confirmation we are clean.

When upstream PR is created, please include its reference in src/native/external/libunwind-version.txt in this PR's branch.

[AustinWise]

This should also fix #100207.

[janvorli]

LGTM, thank you!

[AaronRobinsonMSFT]

@am11 if you could also take another pass at this, I would be most appreciative.

[filipnavara]

Thanks for wrapping this up! LGTM

[am11]

@AaronRobinsonMSFT, looks good but can you please open a PR upstream and reference it in version file? We have been following that pattern for all similar PRs.