RFR: 8343982: Remove usage of security manager from ClassLoader and related classes [v2]

[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 requires special attention.

Alan Bateman has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Change 2-arg findResource to use findResourceOnClassPath when finding resources on class path
 - Merge branch 'master' into JDK-8343982
 - Initial commit

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22097/files
  - new: https://git.openjdk.org/jdk/pull/22097/files/dd2db35b..742fe89c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22097&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22097&range=00-01

  Stats: 525 lines in 30 files changed: 435 ins; 19 del; 71 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