RFR: 8345286: Remove use of SecurityManager API from misc areas [v6]

[Jaikiran Pai]

> Can I please get a review of this change which removes usages of SecurityManager related APIs and some leftover related to SecurityManager changes?
> 
> This addresses https://bugs.openjdk.org/browse/JDK-8345286. Most of these changes are trivial. The `src/java.base/linux/classes/jdk/internal/platform/CgroupUtil.java` used to expose utility methods for dealing with SecurityManager permissions and it was called from a few places. That class is no longer needed with the clean up done in this PR.
> 
> No new tests have been introduced and tier testing is currently in progress.

Jaikiran Pai has updated the pull request incrementally with two additional commits since the last revision:

 - remove unused import
 - replace remaining Paths.get() with Path.of() in the updated files

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22478/files
  - new: https://git.openjdk.org/jdk/pull/22478/files/26df25b2..b018ef09

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22478&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22478&range=04-05

  Stats: 7 lines in 2 files changed: 0 ins; 3 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/22478.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22478/head:pull/22478

PR: https://git.openjdk.org/jdk/pull/22478