RFR: 8340830: Console.readLine() and Console.printf() are mutually blocking [v7]

[Naoto Sato]

> Fixing an issue in Console where write is blocked if other thread is waiting to read, which is caused by unnecessary read/write locks. Removing those would solve the problem, as the read/write synchronization is performed at the StreamEn/Decoder level. One unrelated change is to refactor double-checked locking with LazyConstant.

Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:

  Reflects Justin's review

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Changes:
  - all: https://git.openjdk.org/jdk/pull/29493/files
  - new: https://git.openjdk.org/jdk/pull/29493/files/7edf566e..fed88b18

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29493&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29493&range=05-06

  Stats: 27 lines in 1 file changed: 3 ins; 19 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/29493.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29493/head:pull/29493

PR: https://git.openjdk.org/jdk/pull/29493