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

[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).

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Commit messages:
 - 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: https://git.openjdk.org/jdk/pull/19347/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19347&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332514
  Stats: 39 lines in 3 files changed: 32 ins; 0 del; 7 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