RFR: 8378698: Optimize Base64.Encoder#encodeToString [v2]

[Patrick Strawderman]

> Avoid a byte array copy in encodeToString by using JavaLangAccess#uncheckedNewStringWithLatin1Bytes

Patrick Strawderman has updated the pull request incrementally with one additional commit since the last revision:

  Add JMH benchmark for encodeToString

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Changes:
  - all: https://git.openjdk.org/jdk/pull/29920/files
  - new: https://git.openjdk.org/jdk/pull/29920/files/d007ca46..458236ba

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29920&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29920&range=00-01

  Stats: 54 lines in 1 file changed: 54 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/29920.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29920/head:pull/29920

PR: https://git.openjdk.org/jdk/pull/29920