RFR: 8332885: Clarify failure_handler self-tests [v2]

[Ludvig Janiuk]

> Adding commetns to clarify that the failure_handler selftests are intended to be run manually. Ideally this would include a more thorough description of the exepcted outputs, but this is what I have time to add right now.

Ludvig Janiuk has updated the pull request incrementally with three additional commits since the last revision:

 - styling
 - typo
 - reflow

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/19393/files
  - new: https://git.openjdk.org/jdk/pull/19393/files/26a7be5c..a9d2cab2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19393&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19393&range=00-01

  Stats: 7 lines in 1 file changed: 1 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/19393.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19393/head:pull/19393

PR: https://git.openjdk.org/jdk/pull/19393