RFR: 8315242: G1: Fix -Wconversion warnings around GCDrainStackTargetSize

Tue Aug 29 16:23:23 UTC 2023

Use more precise type and range for `GCDrainStackTargetSize`.

The change to `TASKQUEUE_SIZE` is there, because they are used in the same `MIN2`. (All uses expect `TASKQUEUE_SIZE` to be `uint` as well.)

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Commit messages:
 - g1-uint

Changes: https://git.openjdk.org/jdk/pull/15472/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15472&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315242
  Stats: 9 lines in 4 files changed: 0 ins; 2 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/15472.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15472/head:pull/15472

PR: https://git.openjdk.org/jdk/pull/15472