RFR: 8316662: Remove one allocation per conversion in Double.toString(double) and Float.toString(float) [v4]

[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 four additional commits since the last revision:

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

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15861/files
  - new: https://git.openjdk.org/jdk/pull/15861/files/87e09f38..4308b78f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15861&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15861&range=02-03

  Stats: 1500684 lines in 12654 files changed: 338946 ins; 714685 del; 447053 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