RFR: 8360651: Create OSContainer API for memory limit [v2]

[Severin Gehwolf]

> Please review this small addition to add a new `OSContainer::has_memory_limit()` API (Linux only - as with the entire OSContainer API) in preparation for [JDK-8350596](https://bugs.openjdk.org/browse/JDK-8350596) which proposes to increase the default `MaxRAMPercentage` when this new API returns true. The patch is pretty trivial. It's only the testing which amounts to the most lines in this patch.
> 
> Testing:
> - [x] GHA
> - [x] Hotspot container tests on x86_64 Linux on cgroup v1 and cgroup v2 (including the new tests).
> 
> Thoughts?

Severin Gehwolf has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Merge branch 'master' into jdk-8360651-mem-limit-api
 - MemoryLimitTest whitespace fixes.
 - TestContainerMemory whitespace fixes.
 - 8360651: Create OSContainer API for memory limit

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/26020/files
  - new: https://git.openjdk.org/jdk/pull/26020/files/c1de932d..571de6f3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26020&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26020&range=00-01

  Stats: 128282 lines in 3429 files changed: 76338 ins; 33209 del; 18735 mod
  Patch: https://git.openjdk.org/jdk/pull/26020.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26020/head:pull/26020

PR: https://git.openjdk.org/jdk/pull/26020