Decommit memory as needed

[cshung]

This change makes sure:

1. The mark array is decommitted when we decommit the region, and
2. The region is decommitted if we fail to commit the corresponding mark array.

Fixes#79882

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Issue Details

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null

Author:	cshung
Assignees:	cshung
Labels:	area-GC-coreclr
Milestone:	-

[Maoni0]

also it would be nice to add a comment to delete_region to specify the invariant which is when you return a region to the global region allocator, memory should be decommitted (unless it's large pages) and mark array (if committed).

[PeterSolMS]

Looks good to me.

Regarding Maoni's comment, I wonder if we can add an assert to delete_region to actually enforce the invariant. To make that work, decommit_region would need to set heap_segment_committed for the region, so we know its memory is decommitted.

[Maoni0]

LGTM!

[sebastienros]

With these commits (2ca7cf7...6aaaaaa) aspnet apps crash at runtime in the benchmarks CI. I am flagging the PR which had the potential to explain it.

Crank command if you can run with and without this PR changes:

crank --config https://raw.githubusercontent.com/aspnet/Benchmarks/main/src/BenchmarksApps/Mvc/benchmarks.certapi.yml --config https://raw.githubusercontent.com/aspnet/Benchmarks/main/build/ci.profile.yml --scenario NoMvcAuth --profile intel-win-app --profile intel-load2-load --profile intel-db-db --application.framework net8.0 --application.aspNetCoreVersion 8.0.0-alpha.1.23062.23 --application.runtimeVersion 8.0.0-alpha.1.23061.12 --application.sdkVersion 8.0.100-alpha.1.23061.8