RFR: Backporting related changes [v2]

[Jesper Wilhelmsson]

> Added a section on backporting multiple related changes.
> Replaced "push" with "integrate" in several places since developers can't push to the OpenJDK repositories.
> Removed the JBS label vthreads that has been retired and is no longer in use in JBS.

Jesper Wilhelmsson has updated the pull request incrementally with one additional commit since the last revision:

  Fixed review comments

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Changes:
  - all: https://git.openjdk.org/guide/pull/129/files
  - new: https://git.openjdk.org/guide/pull/129/files/fbbd7113..7a7c0b66

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=guide&pr=129&range=01
 - incr: https://webrevs.openjdk.org/?repo=guide&pr=129&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/guide/pull/129.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/129/head:pull/129

PR: https://git.openjdk.org/guide/pull/129