RFR: 8311939: Excessive allocation of Matcher.groups array [v6]

[Cristian Vat]

> Reduces excessive allocation of Matcher.groups array when the original Pattern has no groups or less than 9 groups.
> 
> Original clamping to 10 possibly due to documented behavior from javadoc: 
> "In this class, \1 through \9 are always interpreted as back references, "
> 
> Only with Matcher changes RegExTest.backRefTest fails when backreferences to non-existing groups are present.
> Added a match failure condition in Pattern that fixes failing tests.
> 
> As per existing `java.util.regex.Pattern.BackRef#match`: "// If the referenced group didn't match, neither can this"
> 
> A group that does not exist in the original Pattern can never match so neither can a backref to that group.
> If the group existed in the original Pattern then it would have had space allocated in Matcher.groups for that group index.
> So a group index outside groups array length must never match.

Cristian Vat 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 six additional commits since the last revision:

 - Merge branch 'openjdk:master' into JDK-8311939
 - review condition
 - changes and test for CIBackRef
 - remove new line
 - reduce allocations also for Matcher.usePattern
 - 8311939: Excessive allocation of Matcher.groups array

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/14894/files
  - new: https://git.openjdk.org/jdk/pull/14894/files/37b18e0c..0538e25e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14894&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14894&range=04-05

  Stats: 64874 lines in 1702 files changed: 33516 ins; 19812 del; 11546 mod
  Patch: https://git.openjdk.org/jdk/pull/14894.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14894/head:pull/14894

PR: https://git.openjdk.org/jdk/pull/14894