RFR: 8302987: Add uniform and spatially equidistributed bounded float/double streams to RandomGenerator

[Raffaello Giulietti]

The `default` method `nextDouble(double origin, double bound)` in `java.util.random.RandomGenerator` aims at generating a uniformly and spatially equidistributed random `double` in the left-closed and right-open range [`origin`, `bound`). It does so by applying the affine transform `origin + (bound - origin) * r` to a uniformly and spatially equidistributed random `double` `r` in the range [0, 1).

Since floating-point arithmetic suffers from small but noticeable rounding errors, this ends up slightly deforming the distribution of `r` when applying the affine transform.

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Commit messages:
 - 8302987: Add uniform and spatially equidistributed bounded float/double streams to RandomGenerator

Changes: https://git.openjdk.org/jdk/pull/12719/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12719&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302987
  Stats: 253 lines in 1 file changed: 251 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/12719.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12719/head:pull/12719

PR: https://git.openjdk.org/jdk/pull/12719