RFR: 8312976: MatchResult produces StringIndexOutOfBoundsException for groups outside match [v2]

[Raffaello Giulietti]

> Fixes a bug showing up after [JDK-8132995](https://bugs.openjdk.org/browse/JDK-8132995) when there are capturing groups outside the match.

Raffaello Giulietti has updated the pull request incrementally with two additional commits since the last revision:

 - Added a test with negatvie lookbehind.
 - Added test with a lookahead containing a back reference.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15053/files
  - new: https://git.openjdk.org/jdk/pull/15053/files/8c737329..2b164c87

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15053&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15053&range=00-01

  Stats: 75 lines in 1 file changed: 75 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15053.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15053/head:pull/15053

PR: https://git.openjdk.org/jdk/pull/15053