RFR: 8345403: Add more randomized tests to better cover FloatingDecimal parsing [v3]

[Joe Darcy]

On Wed, 4 Dec 2024 10:21:57 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>> `jdk.internal.math.FloatingDecimal` parsing is mostly exercised on inputs produced by `Float.toString` and `Double.toString`, but should be extended on more random inputs.
>
> Raffaello Giulietti has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Minors.

Marked as reviewed by darcy (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/22523#pullrequestreview-2480514204