RFR: 8343982: Remove usage of security manager from ClassLoader and related classes

[Alan Bateman]

Remove the code for the now defunct SecurityManager execution mode from ClassLoader and the built-in class loader implementations. The override of getPermissions is removed from the application class loader, and from the class loaders used to support module layers.

URLCassLoader (and its implementation URLClassPath) will be handled separately as there are spec changes required, and code in URLClassPath that require special attention.

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/jdk/pull/22097/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22097&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343982
  Stats: 437 lines in 7 files changed: 6 ins; 361 del; 70 mod
  Patch: https://git.openjdk.org/jdk/pull/22097.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22097/head:pull/22097

PR: https://git.openjdk.org/jdk/pull/22097