More preparation for JIT\Regression test merging (#79697)

More preparation for JIT\Regression test merging (#79697)

This is another collection of changes that can be merged independently of actual test merging. Automated changes were done with the ILTransform tool (started by @trylek, my version at https://github.com/markples/utils/tree/for-PR-dotnet-runtime-79697, commit 6324a32f).

- Remove test JIT/Regression/VS-ia64-JIT/V1.2-Beta1/b102887 (identical to JIT/Regression/VS-ia64-JIT/V1.2-M02/b28077)
- Dedup class names in GitHub_23199
  - JIT/Regression/JitBlue/GitHub_23199 used #ifdefs to create 32 and 64 bit versions of the test
  - Both versions can run on any host
  - Duplicate the test with different names and no ifdefs
  - Run both versions on all hosts
- Merge b399444 into one test that handles both cases
  - JIT/Regression/CLR-x86-JIT/V2.0-Beta2/b399444 used #ifdefs to create two tests
  - Combine both into one test that checks both without #ifdefs
  - Delete unused .xml files
- Add RequiresProcessIsolation
  - Automated via `ILTransform -prociso`
  - Add `<RequiresProcessIsolation>true</RequiresProcessIsolation>` for any test with CLRTestTargetUnsupported, GCStressIncompatible, UnloadabilityIncompatible, JitOptimizationSensitive, TieringTestIncompatible, HeapVerifyIncompatible, IlasmRoundTripIncompatible, SynthesizedPgoIncompatible, or CrossGenTest properties.
  - Add `<RequiresProcessIsolation>true</RequiresProcessIsolation>` for any test with CLRTestBashEnvironmentVariable, CLRTestBatchEnvironmentVariable, CLRTestEnvironmentVariable, Content, CMakeProjectReference (not sure about the last two, but they only impact 3 tests and can be examined later)
  - Add `<RequiresProcessIsolation>true</RequiresProcessIsolation>` for any test that calls Environment.Exit
  - Add comment explaining why RequiresProcessIsolation is set to help with removing them later
- Make entry points public
  - Automated via `ILTransform -public`
  - Update entry point method (`Main` for C#, whatever is marked `.entrypoint` for IL) to be public
  - Update entry point's enclosing type to be public if it exists
  - Wrap IL entry points in a new class if one doesn't exist (e.g., CLR-x86-JIT/V1-M09.5-PDC/b10940/b10940a.il)
- Manual fixes for public changes
  - These were all C# cases where Main was previously in a non-public type with other public methods that contained non-public types
  - Fix in all cases is to just make the other method not public