Fixed a WKS specific issue by not clobbering the heap_segment_saved_allocated

[mrsharm]

For WKS, we weren't using the correct heap_segment_saved_allocated value as it was overwritten in the plan phase and as a result, we didn't compact causing us to fill up the decommit list and continually call virtual_commit and virtual_decommit.

The fix, specifically for WKS, involves not overwriting the value of heap_segment_saved_allocated if it has already been set.

This PR is an effort to fix microbenchmarks that regressed after regions were introduced such as: #67909.

[ghost]

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Issue Details

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For WKS, we weren't using the correct heap_segment_saved_allocated value as it was overwritten in the plan phase and as a result, we didn't compact causing us to fill up the decommit list and continually call virtual_commit and virtual_decommit.

The fix, specifically for WKS, involves not overwriting the value of heap_segment_saved_allocated if it has already been set.

This PR is an effort to fix microbenchmarks that regressed after regions were introduced such as: #67909.

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

[mrsharm]

This PR is ready. I ran the benchmark numbers for the EnumToString benchmark and the numbers are back to those of segments with this change:

Method	value	Mean	Error	StdDev	Median	Min	Max	Gen 0	Allocated
EnumToString	Yellow	13.31 ns	0.274 ns	0.243 ns	13.32 ns	12.90 ns	13.79 ns	0.0023	24 B

In comparison to regions without the fix:

Method	value	Mean	Error	StdDev	Median	Min	Max	Gen 0	Allocated
EnumToString	Yellow	15.75 ns	0.325 ns	0.271 ns	15.70 ns	15.37 ns	16.33 ns	0.0023	24 B

As a baseline, the numbers for Segments were:

Method	value	Mean	Error	StdDev	Median	Min	Max	Gen 0	Allocated
EnumToString	Yellow	13.52 ns	0.270 ns	0.226 ns	13.53 ns	13.15 ns	14.02 ns	0.0023	24 B

[sebastienros]

Can you check this PR is not the source of this issue? #73254
In the meantime, I am trying to reduce the range of commits to help us isolate the actual change.

[EgorBo]

Improvements on
win-arm64: dotnet/perf-autofiling-issues#7144
win-x64: dotnet/perf-autofiling-issues#7175
ubuntu-x64: dotnet/perf-autofiling-issues#7187
win-amd64: dotnet/perf-autofiling-issues#7222
alpiine-x64: dotnet/perf-autofiling-issues#8107