[jdk20] RFR: 8298649: JFR: RemoteRecordingStream support for checkpoint event sizes beyond u4

[Erik Gahlin]

Could I have a review of a follow up fix to [JDK-8298129](https://bugs.openjdk.org/browse/JDK-8298129) to allow check point events with a size larger than u4 to be transferred over JMX.

Testing: jdk/jdk/jfr 

An overflow happens at line 265 if v and payLoadSize is not long values:

payLoadSize += (v << sizeShift);

The field should be renamed to payloadSize, but I will do it separately to keep this change easy to review.

Thanks
Erik

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

Commit messages:
 - Make v long
 - Initial

Changes: https://git.openjdk.org/jdk20/pull/30/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk20&pr=30&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8298649
  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk20/pull/30.diff
  Fetch: git fetch https://git.openjdk.org/jdk20 pull/30/head:pull/30

PR: https://git.openjdk.org/jdk20/pull/30