[jdk25u-dev] RFR: 8370572: Cgroups hierarchical memory limit is not honored after JDK-8322420

[Severin Gehwolf]

Unclean backport of JDK-8370572 since JDK-8292984 is not in 25u (a cleanup patch). That change basically renames `phys_mem` to `upper_bound`. Not really critical to get JDK-8292984 into 25u. What's more, the changes in this patch have the changes done in JDK tip with JDK-8365606 of moving the `if (uses_hierarchy)` inside the branch where the limit is larger than the host limit (upper bound limit). This is the more defensive fix to not fall into the `else` branch should `memory.use_hierarchy` see a `0`.

Please review!

Testing:
- [x] GHA (still running)
- [x] Container tests on Linux x86_64 on cgroups v1 with the test from JDK-8370966 (see dependent PR). Also checked container tests on cgroups v2 for sanity. This patch is a no-op there.

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Commit messages:
 - Backport c49a94bf89876c4d6c777a9452618afa564c5c23

Changes: https://git.openjdk.org/jdk25u-dev/pull/76/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u-dev&pr=76&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370572
  Stats: 33 lines in 3 files changed: 32 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk25u-dev/pull/76.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u-dev.git pull/76/head:pull/76

PR: https://git.openjdk.org/jdk25u-dev/pull/76