<i18n dev> RFR: 8300869: Make use of the Double.toString(double) algorithm in java.util.Formatter

[Raffaello Giulietti]

Align `double` and `float` decimal conversions in `java.util.Formatter` with the algorithm used in `Double.toString(double)`.

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Commit messages:
 - 8300869: Make use of the Double.toString(double) algorithm in java.util.Formatter

Changes: https://git.openjdk.org/jdk/pull/12259/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12259&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300869
  Stats: 720 lines in 4 files changed: 319 ins; 372 del; 29 mod
  Patch: https://git.openjdk.org/jdk/pull/12259.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12259/head:pull/12259

PR: https://git.openjdk.org/jdk/pull/12259