[lworld] RFR: 8370450: [lworld] Alternate implementation of the substitutability test method [v4]

[Frederic Parain]

> This is an alternate version of the substitutability method.
> To use it, add -Xshare:off -XX:+UseAltSubstitutabilityMethod to the command line of the Valhalla VM in preview mode.

Frederic Parain has updated the pull request incrementally with one additional commit since the last revision:

  More fixes uggested in reviews

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1695/files
  - new: https://git.openjdk.org/valhalla/pull/1695/files/22b74040..661ffa7f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1695&range=03
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1695&range=02-03

  Stats: 3 lines in 3 files changed: 0 ins; 1 del; 2 mod
  Patch: https://git.openjdk.org/valhalla/pull/1695.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1695/head:pull/1695

PR: https://git.openjdk.org/valhalla/pull/1695