RFR: 8357218: G1: Remove loop in G1CollectedHeap::try_collect_fullgc

[Albert Mingkun Yang]

Simple removing unnecessary loop in "caller" of `VM_G1CollectFull`, because full-gc always run-to-completion.

Test: tier1-3

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Commit messages:
 - g1-remove-full-gc-loop

Changes: https://git.openjdk.org/jdk/pull/25296/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25296&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357218
  Stats: 24 lines in 3 files changed: 0 ins; 16 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/25296.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25296/head:pull/25296

PR: https://git.openjdk.org/jdk/pull/25296