RFR: More on testing [v2]

[Jesper Wilhelmsson]

> * Added clarifications and expectations around testing and review
> * Moved GHA section (unchanged)
> * Removed outdated stuff from the glossary

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/98/files
  - new: https://git.openjdk.org/guide/pull/98/files/e0959549..1a938bf5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=guide&pr=98&range=01
 - incr: https://webrevs.openjdk.org/?repo=guide&pr=98&range=00-01

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/guide/pull/98.diff
  Fetch: git fetch https://git.openjdk.org/guide pull/98/head:pull/98

PR: https://git.openjdk.org/guide/pull/98