RFR: 8273100: Improve AbstractStringBuilder.append(String) when using CompactStrings [v2]

[Claes Redestad]

> Refactor to improve inlining, which helps some microbenchmarks exer StringBuilder.append(String)

Claes Redestad 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 two additional commits since the last revision:

 - Merge branch 'master' into asb_inlining
 - 8273100: Improve AbstractStringBuilder.append(String) when using CompactStrings

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5291/files
  - new: https://git.openjdk.java.net/jdk/pull/5291/files/56e55c57..e5052256

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5291&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5291&range=00-01

  Stats: 152 lines in 4 files changed: 143 ins; 5 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5291.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5291/head:pull/5291

PR: https://git.openjdk.java.net/jdk/pull/5291