RFR: 8298129: Let checkpoint event sizes grow beyond u4 limit

[Markus Grönlund]

Greetings,

This change pre-calculates the event size for checkpoint / constant pool events (event id 1) before serialization to disk and circumvents the need to reserve a limited checkpoint event size up front, to be later filled in, using a padded write of the actual size. It lets us represent small checkpoint events more effectively, but more importantly, it allows for larger checkpoint / constant pool events because the event size pre-reservation no longer restricts them. The parser side will continue to read checkpoint event sizes as varints, but will expose the checkpoint event size as a long instead of an int.

Testing: jdk_jfr, stress testing

Thanks
Markus

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Commit messages:
 - remove min_intx
 - 8298129

Changes: https://git.openjdk.org/jdk/pull/11584/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11584&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8298129
  Stats: 139 lines in 6 files changed: 84 ins; 17 del; 38 mod
  Patch: https://git.openjdk.org/jdk/pull/11584.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11584/head:pull/11584

PR: https://git.openjdk.org/jdk/pull/11584