RFR: 8311939: Excessive allocation of Matcher.groups array

[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.

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Commit messages:
 - 8311939: Excessive allocation of Matcher.groups array

Changes: https://git.openjdk.org/jdk/pull/14894/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14894&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311939
  Stats: 9 lines in 2 files changed: 7 ins; 1 del; 1 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