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

[Raffaello Giulietti]

On Tue, 3 Dec 2024 18:49:43 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.

All aspects of a syntactically correct input should be randomized.

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PR Comment: https://git.openjdk.org/jdk/pull/22523#issuecomment-2515342957