RFR: JDK-8263261 Extend String::translateEscapes to support unicode escapes [v12]

[Jim Laskey]

> Currently String::translateEscapes does not support unicode escapes, reported as a IllegalArgumentException("Invalid escape sequence: ..."). String::translateEscapes should translate unicode escape sequences to provide full coverage,

Jim Laskey 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 12 additional commits since the last revision:

 - Merge remote-tracking branch 'upstream/master' into 8263261
 - Update unicode to Unicode
 - Requested changes
 - Update String.java
 - Requested changes
 - Update Copyright
 - Update copyright year of test
 - Add JLS Unicode Escapes reference
 - Update comment
 - Update copyright year
 - ... and 2 more: https://git.openjdk.org/jdk/compare/eea3c2d9...040bda82

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Changes:
  - all: https://git.openjdk.org/jdk/pull/17491/files
  - new: https://git.openjdk.org/jdk/pull/17491/files/b57a551d..040bda82

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17491&range=11
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17491&range=10-11

  Stats: 8261 lines in 340 files changed: 5165 ins; 1908 del; 1188 mod
  Patch: https://git.openjdk.org/jdk/pull/17491.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17491/head:pull/17491

PR: https://git.openjdk.org/jdk/pull/17491