[SOS/DAC] Add tests for DAC GC bugs

[max-charlamb]

• DumpGCData
  • This test currently fails on server builds due to a bug in the DAC.
  • Fixed by [DAC] fix dac_gc_heap marshalling runtime#119393
• FindRootsOlderGeneration
  • Test fails on main branch due to improper dereferncing in the DAC.
  • Fixed by [DAC] Properly dereference internal_root_array runtime#119396

[davidwrighton]

I believe we need to have a scheme to disable this test for versions of the runtime older than .NET 11 (unless of course you intend to fix this in downlevel versions), but this looks generally ok to me.

[steveisok]

I believe we need to have a scheme to disable this test for versions of the runtime older than .NET 11 (unless of course you intend to fix this in downlevel versions), but this looks generally ok to me.

diagnostics/src/SOS/SOS.UnitTests/SOS.cs

Line 206 in a853665

if (config.RuntimeFrameworkVersionMajor < 10)

is an example of how to pull that off.

[noahfalk]

Looks good! Comments inline where I'm hoping we can simplify the config pattern.

[max-charlamb]

I found this bug while working on the tests. In some cases, this is not initialized before referencing.