[Pinned Object Heap] `DAC_NUMBERGENERATIONS` may need to be adjusted

[VSadov]

DAC_NUMBERGENERATIONS is currently 4 and changing it is a compat issue.

We should think what to do with this.

Merge POH into LOH data, have a separate field, etc...

[mikem8361]

The existing DacpGcHeapDetails request and DacpGenerationAllocData Request APIs have to be backwards compatible with DAC_NUMBERGENERATIONS = 4. They could return the generations that are similar to the old 0 - 4 generations (I don't know how enough about the GC to really say).

New APIs should be added that return N (instead of a fixed number) generations somehow. There would be a lot of changes to SOS required to use these new APIs. Probably to clrmd too.

[tommcdon]

@VSadov do you plan on addressing this issue in .NET 5 timeframe?

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[VSadov]

Yes, the plan is to address this for 5.0
From the feedback I hear that this should be addressed sooner rather than later. I'll try to get to this this week.

[davmason]

@VSadov have you had a chance to work on this yet? We're getting close to the feature complete date and I haven't seen any changes.

[Maoni0]

API to get # of generations added via this PR

[davmason]

Fixed in #37853