RFR: 8349176: Speed up Integer/Long.toString via StringConcatHelper::newArray [v4]

[Shaojin Wen]

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

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

  use Unsafe::allocateUninitializedArray

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Changes:
  - all: https://git.openjdk.org/jdk/pull/23353/files
  - new: https://git.openjdk.org/jdk/pull/23353/files/d6942080..549ff0f8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23353&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23353&range=02-03

  Stats: 6 lines in 2 files changed: 2 ins; 0 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