RFR: 7992: Add API to easily write annotated Java JFR events [v4]

[Jaroslav Bachorik]

> This PR extends the JFR Writer API with the ability to use the custom JFR event types (eg. classes extending `jdk.jfr.Event`) and register new writer type for them and also directly accept the instances of those types to write them in the recording.

Jaroslav Bachorik has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains ten additional commits since the last revision:

 - Replace commented out println with logger
 - Merge remote-tracking branch 'upstream/master' into jb/JMC-7992
 - Add unit tests for using custom events directly in the writer API
 - Improve handling of the overriden internal fields
 - Merge branch 'master' into jb/JMC-7992
 - Add more explanatory comments
 - Add javadoc for the new public methods
 - Update copyright year
 - JMC-7992: Add API to easily write annotated Java JFR events

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Changes:
  - all: https://git.openjdk.org/jmc/pull/457/files
  - new: https://git.openjdk.org/jmc/pull/457/files/5bd8c044..8b50e795

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jmc&pr=457&range=03
 - incr: https://webrevs.openjdk.org/?repo=jmc&pr=457&range=02-03

  Stats: 2899 lines in 209 files changed: 1732 ins; 759 del; 408 mod
  Patch: https://git.openjdk.org/jmc/pull/457.diff
  Fetch: git fetch https://git.openjdk.org/jmc.git pull/457/head:pull/457

PR: https://git.openjdk.org/jmc/pull/457