RFR: 8336679: Add @implSpec for the default implementations in Process.waitFor() [v2]

[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:

  Addressing a CSR comment

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20285/files
  - new: https://git.openjdk.org/jdk/pull/20285/files/bd91aba2..49b894b6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20285&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20285&range=00-01

  Stats: 8 lines in 1 file changed: 2 ins; 0 del; 6 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