RFR: 8336679: Add @implSpec for the default implementations in Process.waitFor() [v3]

[Naoto Sato]

> This is a simple doc-only change that follows up [JDK-8336479](https://bugs.openjdk.org/browse/JDK-8336479). A corresponding CSR has also been drafted.

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

  apiNote -> implNote

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/20285/files
  - new: https://git.openjdk.org/jdk/pull/20285/files/49b894b6..17c61d99

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20285&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20285&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/20285.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20285/head:pull/20285

PR: https://git.openjdk.org/jdk/pull/20285