RFR: 8315580: Remove unused java_lang_String::set_value_raw() [v2]

[Kim Barrett]

> Please review this trivial change to remove the unused function java_lang_String::set_value_raw.
> 
> Testing:
> mach5 tier1

Kim Barrett 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 set-value-raw
 - remove unused function

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15552/files
  - new: https://git.openjdk.org/jdk/pull/15552/files/baa152dc..5f14e40a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15552&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15552&range=00-01

  Stats: 22741 lines in 747 files changed: 12827 ins; 6763 del; 3151 mod
  Patch: https://git.openjdk.org/jdk/pull/15552.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15552/head:pull/15552

PR: https://git.openjdk.org/jdk/pull/15552