RFR: 8302744: Refactor Hotspot container detection code [v4]

[Severin Gehwolf]

> Please review this container detection code refactoring in hotspot. The main point of this is to
> 
> - get rid of the `GET_CONTAINER_INFO` macros which hide too many things under the hood
> - prevent refactoring of the code (since `GET_CONTAINER_INFO` macros short-return and are therefore not portable; at least not without some risk)
> - make the code easier to understand
> - allow for better testing via `gtest`
> - separate multi-line parsing from single line parsing for clarity.
> 
> Testing:
> - [x] GHA
> - [x] `gtest:cgroupTest` tests
> - [x] Container tests on Linux with cgroup v1 (legacy) and cgroup v2. All pass.
> 
> Thoughts?

Severin Gehwolf has updated the pull request incrementally with four additional commits since the last revision:

 - Make read_string() take the output buffer size
 - Fix style for read_numerical_key_value
 - Use assertions for required parameters
 - Use boolean for tuples

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/19060/files
  - new: https://git.openjdk.org/jdk/pull/19060/files/c41d3183..e41b5f6b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19060&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19060&range=02-03

  Stats: 128 lines in 5 files changed: 23 ins; 48 del; 57 mod
  Patch: https://git.openjdk.org/jdk/pull/19060.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19060/head:pull/19060

PR: https://git.openjdk.org/jdk/pull/19060