[lworld] RFR: 8372954: [lworld] Remove old implementation of the substitutability test method [v3]

[Paul Hübner]

> Hi all,
> 
> This change removes the old substitutability test method. The new/alt substitutability test takes the place of the legacy test, and all identifiers with "alt" are removed.
> 
> Testing: tiers 1-5 on Linux (x64, AArch64), macOS (x64, AArch64), Windows (x64).

Paul Hübner 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 13 additional commits since the last revision:

 - Merge branch 'lworld' of https://github.com/openjdk/valhalla into JDK-8372954
 - Missed obsolete test
 - Years
 - Merge branch 'lworld' of https://github.com/openjdk/valhalla into JDK-8372954
 - substitutability contract changed
 - Legacy handling in ProcessHandleImpl
 - typo
 - Test flags
 - Dead stuff
 - Merge branch 'JDK-8372954' of github.com:Arraying/valhalla into JDK-8372954
 - ... and 3 more: https://git.openjdk.org/valhalla/compare/708770ec...29344379

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/2012/files
  - new: https://git.openjdk.org/valhalla/pull/2012/files/34e7ea45..29344379

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=2012&range=02
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=2012&range=01-02

  Stats: 963 lines in 27 files changed: 792 ins; 80 del; 91 mod
  Patch: https://git.openjdk.org/valhalla/pull/2012.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2012/head:pull/2012

PR: https://git.openjdk.org/valhalla/pull/2012