RFR: 8344223: Remove calls to SecurityManager and doPrivileged in java.net.URLClassLoader after JEP 486 integration [v3]

[Jaikiran Pai]

> Can I please get a review of this change which proposes to remove SecurityManager related API usages from `URLClassLoader` and its related `URLClassPath`? This addresses https://bugs.openjdk.org/browse/JDK-8344223.
> 
> The `URLClassLoader.getPermissions()` method will need additional changes but that will be done as part of https://bugs.openjdk.org/browse/JDK-8343150.
> 
> I'll be opening a CSR for this change because we are removing support for the `jdk.net.URLClassPath.disableRestrictedPermissions` system property.
> 
> No new tests have been added and existing tier1, tier2 and tier3 tests continue to pass.

Jaikiran Pai has updated the pull request incrementally with one additional commit since the last revision:

  Alan's review - fix code comment

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22233/files
  - new: https://git.openjdk.org/jdk/pull/22233/files/5a82b729..1c26dbf2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22233&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22233&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/22233.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22233/head:pull/22233

PR: https://git.openjdk.org/jdk/pull/22233