RFR: 8349176: Speed up Integer/Long.toString via Unsafe.allocateUninitializedArray [v2]

[Shaojin Wen]

> The byte[] allocated in Integer/Long.toString is fully filled, so we can use Unsafe.allocateUninitializedArray to create byte[] to improve performance.

Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:

  use StringConcatHelper.newArray

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23353/files
  - new: https://git.openjdk.org/jdk/pull/23353/files/2a06d12f..82e0c387

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23353&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23353&range=00-01

  Stats: 8 lines in 2 files changed: 0 ins; 4 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/23353.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23353/head:pull/23353

PR: https://git.openjdk.org/jdk/pull/23353