RFR: 8300658: memory_and_swap_limit() reporting wrong values on systems with swapaccount=0 [v2]

[Severin Gehwolf]

> Please review this change which brings the hotspot code up to date with how the Java metrics behave. On a system where swap accounting is disabled `VM.info` jcmd - for example - no longer reports an unsupported metric, but the memory limit instead as that is actually what is being in place.
> 
> I had to update the `TestMemoryWithCgroupV1.java` test as it skipped the swappiness testing based on the now gone output.
> 
> Testing:
> - [x] Linux container tests on cg1 and cg2 with and without swap accounting.
> - [x] New regression test fails on unpatched systems with `swapaccount=0` kernel option. Passes after.
> - [x] GHA (windows tier1 failure is unrelated).
> 
> Thoughts?

Severin Gehwolf has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:

 - Read mem swap as julong as before
 - Whitespace fix-up after merge
 - Merge branch 'master' into jdk-8300658-memory-swap-hs-fix
 - 8300658: memory_and_swap_limit() reporting wrong values on systems with swapaccount=0

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Changes: https://git.openjdk.org/jdk/pull/12262/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12262&range=01
  Stats: 55 lines in 5 files changed: 51 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/12262.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12262/head:pull/12262

PR: https://git.openjdk.org/jdk/pull/12262