RFR: 8376051: gc/stress/TestStressG1Uncommit.java fails assertLessThan: expected that xxx < xxx [v2]

[SendaoYan]

> Hi all,
> 
> [JDK-8238686](https://bugs.openjdk.org/browse/JDK-8238686) change the default value MinHeapFreeRatio/MaxHeapFreeRatio to 0/100, this change make G1 never uncommit heap memory to OS system, this will make test test/hotspot/jtreg/gc/stress/TestStressG1Uncommit.java fails "assertLessThan: expected that xxx < xxx", and the tested java process never print "Uncommit regions" which checked by this test.
> 
> This PR set MinHeapFreeRatio/MaxHeapFreeRatio to the original value 40/70 to make this test work expectly.
> 
> Change has been verified locally on linux-x64 by run this tests both with release build and fastdebug build.

SendaoYan has updated the pull request incrementally with one additional commit since the last revision:

  Revert the use of WhiteBox.fullGC()

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29357/files
  - new: https://git.openjdk.org/jdk/pull/29357/files/6083d958..9035a0b3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29357&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29357&range=00-01

  Stats: 11 lines in 1 file changed: 0 ins; 9 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/29357.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29357/head:pull/29357

PR: https://git.openjdk.org/jdk/pull/29357