Delete -fms-extensions from coreclr native build

[am11]

For stdcpp conformance, remove the remaining special extensions.

• clean up unnecessary __llvm special handling.
• Add class, enum, struct prefixes to cases where the variable name is clashing with type name and it changes meaning (-Werror=changes-meaning)
  • In some trivial cases, I just renamed the variables..
• On x86, replace __asm {} syntax with __asm ("")
• Two small illumos related build fixes under src/native which helped validating the rest of the changes on the platform.

[dotnet-policy-service]

Tagging subscribers to this area: @hoyosjs
See info in area-owners.md if you want to be subscribed.

[janvorli]

I wonder why it was defined differently for x86. @jkotas do you have any idea?

[jkotas]

Historically, inline int 3 gave a better experience under the debugger - the debugger stopped in your code, not inside a Windows DebugBreak API.

[am11]

OSX failure is infra issue (tests are passing but helix job is unable to exit cleanly):

/private/tmp/helix/working/A8E70893/w/A68408BE/e /private/tmp/helix/working/A8E70893/w/A68408BE/e
  Discovering: System.Text.RegularExpressions.Unit.Tests (method display = ClassAndMethod, method display options = None)
  Discovered:  System.Text.RegularExpressions.Unit.Tests (found 25 test cases)
  Starting:    System.Text.RegularExpressions.Unit.Tests (parallel test collections = on [12 threads], stop on fail = off)
  Finished:    System.Text.RegularExpressions.Unit.Tests
=== TEST EXECUTION SUMMARY ===
   System.Text.RegularExpressions.Unit.Tests  Total: 830, Errors: 0, Failed: 0, Skipped: 0, Time: 0.352s
/private/tmp/helix/working/A8E70893/w/A68408BE/e
----- end Wed Jun 12 17:28:07 EDT 2024 ----- exit code 0 ----------------------------------------------------------
exit code 0 means Exited Successfully
Unable to obtain kernel buffer: Operation not permitted
usage: sudo dmesg
----- start =============== XUnitLogChecker Output =====================================================
No dumps found in /cores.

rest of failures are known issues (per Build Analysis).

@jkotas, PTAL.

[jkotas]

Thank you!