RFR: 8082: Add ctrl+a keyboard shortcut to select all lanes on jfr threads page [v2]

[Alex Macdonald]

> This PR addresses JMC-8082 [[0]](https://bugs.openjdk.org/browse/JMC-8082), in which it'd be nice to easily select all the threads on the jfr threads page using a keyboard shortcut. Inspired by https://github.com/openjdk/jmc/pull/492, it would be nice to add more "table" behaviour to the jfr threads page text canvas. In this case, the keyboard shortcut ctrl+a will highlight all of the thread lanes and update the current selection.
> 
> [0] https://bugs.openjdk.org/browse/JMC-8082

Alex Macdonald has updated the pull request incrementally with one additional commit since the last revision:

  make spotless happy

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Changes:
  - all: https://git.openjdk.org/jmc/pull/493/files
  - new: https://git.openjdk.org/jmc/pull/493/files/9da24616..125207dd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jmc&pr=493&range=01
 - incr: https://webrevs.openjdk.org/?repo=jmc&pr=493&range=00-01

  Stats: 6 lines in 2 files changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jmc/pull/493.diff
  Fetch: git fetch https://git.openjdk.org/jmc.git pull/493/head:pull/493

PR: https://git.openjdk.org/jmc/pull/493