Improve CPU metrics calculations for CgroupV2

[nivebb8]

Microsoft Reviewers: Open in CodeFlow

Problem Statement:

1. Current code is always assuming that container cgroup is at fixed location (/sys/fs/cgroup), which may not be the case always. The correct cgroup path should be retrieved from "/proc/self/cgroup" file.
   
2. We are using delta Host CPU for containers % of usages. A better option would be to use cpu limits (cpu.max) set by the Cgroups itself. Host CPU delta might change due to factors other than the container usages.

[nivebb8]

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[evgenyfedorov2]

I understand this is still in Draft state, but just a note - we will need to some Acceptance tests, similar to already existing one, where we emulate filesystem and test the library as a whole

[swapniliit2222]

Added few review comments

[evgenyfedorov2]

Can we please have a test similar to this (of course we don't have to compare values with Tracker). The test will validate that the new logic picks up changes from file system as expected

[nivebb8]

Can we please have a test similar to this (of course we don't have to compare values with Tracker). The test will validate that the new logic picks up changes from file system as expected

Added

[joperezr]

/backport to release/9.4

[github-actions]

Started backporting to release/9.4: https://github.com/dotnet/extensions/actions/runs/14520112091