RFR: 8370950: Inline CollectedHeap::fill_args_check

[Albert Mingkun Yang]

Trivial inlining a method to reduce API surface.

Test: tier1

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Commit messages:
 - trivial-inline

Changes: https://git.openjdk.org/jdk/pull/28061/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28061&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370950
  Stats: 11 lines in 2 files changed: 2 ins; 7 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/28061.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28061/head:pull/28061

PR: https://git.openjdk.org/jdk/pull/28061