[master] RFR: 8347710: [Lilliput] Implement 4 byte headers [v6]

[Roman Kennke]

> Packs/reduces header bits to just 4 bytes.
> 
> This reduces the number of Klass* bits to 19 bits, which allows for ~500,000 classes.
> 
> Testing:
> 
> - tier1 (-UCOH)
> - tier2 (-UCOH)
> - tier1 (+UCOH)
> - tier2 (+UCOH)

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

  Comment-out unimplemented RISCV parts

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

Changes:
  - all: https://git.openjdk.org/lilliput/pull/193/files
  - new: https://git.openjdk.org/lilliput/pull/193/files/16702484..81c71cac

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=lilliput&pr=193&range=05
 - incr: https://webrevs.openjdk.org/?repo=lilliput&pr=193&range=04-05

  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/lilliput/pull/193.diff
  Fetch: git fetch https://git.openjdk.org/lilliput.git pull/193/head:pull/193

PR: https://git.openjdk.org/lilliput/pull/193