RFR: 8343453: Modernize FloatingDecimal tests [v3]

[Raffaello Giulietti]

> Simplify tests.

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 five additional commits since the last revision:

 - Cosmetic change.
 - Merge branch 'master' into 8343453
 - Remove test jdk/jdk/internal/math/ToString.java as well.
 - Merge branch 'master' into 8343453
 - 8343453: Modernize FloatingDecimal tests

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/21840/files
  - new: https://git.openjdk.org/jdk/pull/21840/files/e1f8b895..43d6b5a5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21840&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21840&range=01-02

  Stats: 239072 lines in 3462 files changed: 131612 ins; 80588 del; 26872 mod
  Patch: https://git.openjdk.org/jdk/pull/21840.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21840/head:pull/21840

PR: https://git.openjdk.org/jdk/pull/21840