[lworld] RFR: 8372954: [lworld] Remove old implementation of the substitutability test method [v5]

[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 incrementally with two additional commits since the last revision:

 - Silly typo
 - Improve comment, refer to where they are injected

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/2012/files
  - new: https://git.openjdk.org/valhalla/pull/2012/files/cdce2b10..1b17a2f2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=2012&range=04
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=2012&range=03-04

  Stats: 9 lines in 1 file changed: 2 ins; 0 del; 7 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