RFR: 8332514: Allow class space size to be larger than 3GB [v2]

[Thomas Stuefe]

> Class space size is capped at 3GB. Technically, the Klass encoding range is 4GB.
> 
> We cap class space at 3GB to leave breathing room for CDS. However, CDS needs a lot less, so we waste address space. In addition, class space is unnecessarily capped at 3GB even if we run without CDS, which is unnecessary.
> 
> What we should do instead:
> - if CDS is off, use the full 4GB
> - if CDS is on, use as much memory as we can after accommodating the archive
> 
> This patch implements that new behavior. 
> 
> Now, we can have 4GB class space without CDS; with CDS, a bit less (depends on the CDS archive size; by default, on MacOS, we reach about 3.98GB).

Thomas Stuefe 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:

 - Remarks Ioi
 - Merge branch 'master' into JDK-8332514-Allow-class-space-size-to-be-larger-than-3GB-if-possible
 - fix 32-bit (why is this not a 64-bit only option)
 - JDK-8332514-Allow-class-space-size-to-be-larger-than-3GB-if-possible

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/19347/files
  - new: https://git.openjdk.org/jdk/pull/19347/files/ba013f2f..2d33ad47

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19347&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19347&range=00-01

  Stats: 17778 lines in 498 files changed: 11161 ins; 3624 del; 2993 mod
  Patch: https://git.openjdk.org/jdk/pull/19347.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19347/head:pull/19347

PR: https://git.openjdk.org/jdk/pull/19347