RFR: 8313552: Fix -Wconversion warnings in JFR code [v2]

[Markus Grönlund]

> Greetings,
> 
> this change set removes -Wconversion warnings in the JFR code.
> 
> Testing: jdk_jfr
> 
> Thanks
> Markus

Markus Grönlund has updated the pull request incrementally with two additional commits since the last revision:

 - remove compile flag
 - checked_cast

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15152/files
  - new: https://git.openjdk.org/jdk/pull/15152/files/c790ecfa..5c9e1ffe

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15152&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15152&range=00-01

  Stats: 95 lines in 10 files changed: 0 ins; 0 del; 95 mod
  Patch: https://git.openjdk.org/jdk/pull/15152.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15152/head:pull/15152

PR: https://git.openjdk.org/jdk/pull/15152