RFR: 8316662: Remove one allocation per conversion in Double.toString(double) and Float.toString(float) [v2]

[Raffaello Giulietti]

> By correctly sizing an intermediate `byte[]` and making use of the internal `newStringNoRepl()` method, one allocation per conversion can be avoided when the runtime uses compact strings.

Raffaello Giulietti has updated the pull request incrementally with one additional commit since the last revision:

  Uppercase JLA.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15861/files
  - new: https://git.openjdk.org/jdk/pull/15861/files/97f0c7b4..092c2046

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15861&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15861&range=00-01

  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/15861.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15861/head:pull/15861

PR: https://git.openjdk.org/jdk/pull/15861