RFR: 8358540: Enhance MathUtils in view of FloatingDecimal enhancements

[Raffaello Giulietti]

Another step in enhancing floating-point <-> decimal conversions.

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Commit messages:
 - 8358540: Enhance MathUtils in view of FloatingDecimal enhancements

Changes: https://git.openjdk.org/jdk/pull/25641/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25641&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8358540
  Stats: 1781 lines in 8 files changed: 343 ins; 481 del; 957 mod
  Patch: https://git.openjdk.org/jdk/pull/25641.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25641/head:pull/25641

PR: https://git.openjdk.org/jdk/pull/25641