RFR: 8274788: Support archived heap objects in ParallelGC [v2]

[Calvin Cheung]

> With this change when the UseParallelGC is enabled, the CDS archived heap objects could be loaded
> into the PSOldGen during VM bootstrap. This improves startup time since the module graph could be
> loaded from the archive.
> 
> 
> $ perf stat -r 40 -XX:+UseParallelGC -version
> 
> before: 0.069244290 seconds time elapsed            ( +-  0.49% )
> after:    0.058555167 seconds time elapsed          ( +-  0.49% )
> 
> Passed CI tiers 1 - 4 tests.
> 
> Thanks @tschatzl for his help on GC changes.

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

  update copyright header

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7655/files
  - new: https://git.openjdk.java.net/jdk/pull/7655/files/350a1300..658e6e79

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7655&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7655&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7655.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7655/head:pull/7655

PR: https://git.openjdk.java.net/jdk/pull/7655