RFR: 8291598: Matcher.appendReplacement should not create new StringBuilder instances [v3]

[Raffaello Giulietti]

> Remove instantiation of `StringBuilder`

Raffaello Giulietti has updated the pull request incrementally with one additional commit since the last revision:

  8291598: Matcher.appendReplacement should not create new StringBuilder instances
  
  Removed other allocations of StringBuilder when processing named groups in replacement string.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13048/files
  - new: https://git.openjdk.org/jdk/pull/13048/files/c9432a69..4b5ac595

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13048&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13048&range=01-02

  Stats: 4 lines in 1 file changed: 0 ins; 1 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/13048.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/13048/head:pull/13048

PR: https://git.openjdk.org/jdk/pull/13048