RFR: 8344236: Revisit SecurityManager usage in jdk.net after JEP 486 integration

[Jaikiran Pai]

Can I please get a review of this change which removes the usages of `SecurityManager` related APIs from the `jdk.net` module? This addresses https://bugs.openjdk.org/browse/JDK-8344236.

No new tests have been added and existing tests in tier1, tier2 and tier3 have completed without any related failures.

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Commit messages:
 - 8344236: Revisit SecurityManager usage in jdk.net after JEP 486 integration

Changes: https://git.openjdk.org/jdk/pull/22274/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22274&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344236
  Stats: 55 lines in 5 files changed: 0 ins; 43 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/22274.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22274/head:pull/22274

PR: https://git.openjdk.org/jdk/pull/22274