RFR: 8344078: Remove security manager dependency in java.nio [v5]

[Brian Burkhalter]

> Expunge the use of the `SecurityManager`, `AccessController`, and the like from the `java.nio` and `sun.nio` package hierarchies.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8344078: Remove one straggling toString()

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Changes:
  - all: https://git.openjdk.org/jdk/pull/22132/files
  - new: https://git.openjdk.org/jdk/pull/22132/files/bc563aee..7b7f23cf

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22132&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22132&range=03-04

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/22132.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22132/head:pull/22132

PR: https://git.openjdk.org/jdk/pull/22132