[Mono] Synchronize mono's GCMemoryInfo.MemoryLoadBytes with CoreCLR changes

[naricc]

CorCLR changed the calculation of GCMemoryInfo.MemoryLoadBytes in this PR:
#64128. The same underlying problem most likely exists for mono (I haven't verified this yet, but based on the implementation, this is likely), and it should be updated to be in sync with CoreCLR.

This can probably be done by porting some changes from mono/mono: mono/mono#21280 and mono/mono#21503

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Issue Details

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CorCLR changed the calculation of GCMemoryInfo.MemoryLoadBytes in this PR:
#64128. The same underlying problem most likely exists for mono (I haven't verified this yet, but based on the implementation, this is likely), and it should be updated to be in sync with CoreCLR.

Author:	naricc
Assignees:	-
Labels:	area-GC-mono
Milestone:	-

[uweigand]

Looks like this is related to: #58706 - FYI @nealef

[nealef]

Looks like this is related to: #58706 - FYI @nealef

#74237

[akoeplinger]

#74237 was merged, should we keep this open to track unifying the implementations between CoreCLR and Mono as @lambdageek suggested in the PR?