RFR: 8316662: Remove one allocation per conversion in Double.toString(double) and Float.toString(float) [v3]

[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 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 three additional commits since the last revision:

 - Merge branch 'master' into 8316662
 - Uppercase JLA.
 - 8316662: Remove one allocation per conversion in Double.toString(double) and Float.toString(float)

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15861/files
  - new: https://git.openjdk.org/jdk/pull/15861/files/092c2046..87e09f38

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15861&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15861&range=01-02

  Stats: 66648 lines in 2489 files changed: 41106 ins; 11953 del; 13589 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