[jdk21u-dev] RFR: 8325730: StringBuilder.toString allocation for the empty String [v2]

[Aleksey Shipilev]

> Clean backport to resolve the regression introduced in JDK 19.
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `all`

Aleksey Shipilev 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 JDK-8325730-string-empty
 - Backport d2590c69b4efe5aa2b48b08070e0dbafb04ef202

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

Changes:
  - all: https://git.openjdk.org/jdk21u-dev/pull/364/files
  - new: https://git.openjdk.org/jdk21u-dev/pull/364/files/0f183405..8393e8f6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=364&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=364&range=00-01

  Stats: 22536 lines in 583 files changed: 10648 ins; 6643 del; 5245 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/364.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/364/head:pull/364

PR: https://git.openjdk.org/jdk21u-dev/pull/364