RFR: 8293121: (fs) Refactor UnixFileSystem copying into generic Unix, Linux, and BSD implementations

Wed Aug 31 02:38:03 UTC 2022

Refactor `UnixFileSystem` and related classes to move implementations specific to Linux and BSD (macOS) into OS-specific classes and native code. Generic Unix implementations remain in existing `Unix*` files.

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Commit messages:
 - 8293121: (fs) Refactor UnixFileSystem copying into generic Unix, Linux, and BSD implementations

Changes: https://git.openjdk.org/jdk/pull/10093/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10093&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293121
  Stats: 789 lines in 14 files changed: 551 ins; 148 del; 90 mod
  Patch: https://git.openjdk.org/jdk/pull/10093.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10093/head:pull/10093

PR: https://git.openjdk.org/jdk/pull/10093