RFR: 8344337: SecurityManager cleanup in java.prefs module [v6]

[Brent Christian]

> Remove usages of SecurityManager, doPrivildged, and AccessController from the java.prefs module.

Brent Christian has updated the pull request incrementally with one additional commit since the last revision:

  spacing changes

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Changes:
  - all: https://git.openjdk.org/jdk/pull/22252/files
  - new: https://git.openjdk.org/jdk/pull/22252/files/cddc4e2f..10d3cb4f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22252&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22252&range=04-05

  Stats: 19 lines in 1 file changed: 1 ins; 0 del; 18 mod
  Patch: https://git.openjdk.org/jdk/pull/22252.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22252/head:pull/22252

PR: https://git.openjdk.org/jdk/pull/22252