RFR: 8301578: Perform output outside synchronization in Module.class [v4]

[Per Minborg]

> This PR proposed to reduce contention in synchronized methods mainly by doing I/O operations outside synch blocks.

Per Minborg has updated the pull request incrementally with one additional commit since the last revision:

  Use Unsafe instead of synchronized

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12193/files
  - new: https://git.openjdk.org/jdk/pull/12193/files/b0aeb64b..11db7d10

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12193&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12193&range=02-03

  Stats: 65 lines in 1 file changed: 18 ins; 22 del; 25 mod
  Patch: https://git.openjdk.org/jdk/pull/12193.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12193/head:pull/12193

PR: https://git.openjdk.org/jdk/pull/12193