RFR: 8328278: Serial: Compute tenuring threshold before GC [v2]

[Guoxiong Li]

> Hi all,
> 
> This patch places the SerialGC code that computes tenuring threshold before per GC instead of after per GC, so that the method `AgeTable::print_on` prints the right tenuring threshold. Just like the current G1 implementation.
> 
> Thanks for taking the time to review.
> 
> Best Regards,
> -- Guoxiong

Guoxiong Li has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Do not print threshold.
 - Merge branch 'master' into SERIAL_GC_AGE_TABLE
 - Revert.
 - JDK-8328278

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/18329/files
  - new: https://git.openjdk.org/jdk/pull/18329/files/3856d231..d8945592

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18329&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18329&range=00-01

  Stats: 341328 lines in 2577 files changed: 11036 ins; 7583 del; 322709 mod
  Patch: https://git.openjdk.org/jdk/pull/18329.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18329/head:pull/18329

PR: https://git.openjdk.org/jdk/pull/18329