RFR: 8310994: Add JFR event for selection operations [v3]

[Tim Prinzing]

> Added mirror event with static methods: jdk.internal.event.SelectionEvent that provides the duration of select calls and the count of how many keys are available.
> 
> Emit the event from SelectorImpl::lockAndDoSelect
> 
> Test at jdk.jfr.event.io.TestSelectionEvents

Tim Prinzing has updated the pull request incrementally with one additional commit since the last revision:

  add select timeout field to the event

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16710/files
  - new: https://git.openjdk.org/jdk/pull/16710/files/2f7dafd8..13262293

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16710&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16710&range=01-02

  Stats: 21 lines in 4 files changed: 12 ins; 3 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/16710.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16710/head:pull/16710

PR: https://git.openjdk.org/jdk/pull/16710