[jdk21u] RFR: 8313262: C2: Sinking node may cause required cast to be dropped

[Aleksey Shipilev]

Clean backport to fix recent JDK 21 backport regression.

Additional testing:
 - [x] New test fails without the fix, passes with it
 - [ ] Linux x86_64 fastdebug `tier1 tier2 tier3`

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

Commit messages:
 - Backport 1cee3b9fd9720e7938029a6992460b9053e65e57

Changes: https://git.openjdk.org/jdk21u/pull/99/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=99&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313262
  Stats: 69 lines in 2 files changed: 68 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u/pull/99.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/99/head:pull/99

PR: https://git.openjdk.org/jdk21u/pull/99