RFR: 8280029: G1: "Overflow during reference processing, can not continue" on x86_32

[Aleksey Shipilev]

This should fix the intermittent G1 x86_32 failure in GHA. See more investigation in the bug. I think at this point we are better off bumping the default mark stack size for 32-bit builds. Also fix the error message to be less misleading.

Additional testing:
  - [x] Affected test on Linux fastdebug x86_32, 100 repeats; used to fail at about 10th iteration, does not fail anymore;
  - [x] Linux x86_32 fastdebug `tier1`
  - [ ] Linux x86_32 fastdebug `tier2`
  - [ ] Linux x86_32 fastdebug `tier3`

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Commit messages:
 - Touch-up warning
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/7109/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7109&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280029
  Stats: 5 lines in 2 files changed: 1 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7109.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7109/head:pull/7109

PR: https://git.openjdk.java.net/jdk/pull/7109