RFR: 8373566: Performance regression with java.text.MessageFormat subformat patterns [v2]

[Justin Lu]

> This PR addresses a performance degradation when constructing a new MessageFormat that contains a subformat with a pattern that is not a predefined style. This is due to internal logic which catches an IAE specifically for subformat patterns. Perf tests for choice and number are not grouped, since performance is directly tied to subformat creation.
> 
> M1 Mac - Perf (before):
> 
> 
> MessageFormatterBench.testSubformatChoice  thrpt   15   865.430 ±  6.766  ops/ms
> MessageFormatterBench.testSubformatNumber  thrpt   15  1021.808 ± 11.413  ops/ms
> 
> 
> M1 Mac - Perf (after):
> 
> 
> Benchmark                                   Mode  Cnt     Score    Error   Units
> MessageFormatterBench.testSubformatChoice  thrpt   15  1671.033 ± 55.012  ops/ms
> MessageFormatterBench.testSubformatNumber  thrpt   15  3275.727 ± 47.370  ops/ms

Justin Lu has updated the pull request incrementally with one additional commit since the last revision:

  pull values() into a var

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28806/files
  - new: https://git.openjdk.org/jdk/pull/28806/files/702b35f9..8eea336f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28806&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28806&range=00-01

  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/28806.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28806/head:pull/28806

PR: https://git.openjdk.org/jdk/pull/28806