RFR: 8319174: Enhance robustness of some j.m.BigInteger constructors [v2]

[Raffaello Giulietti]

> Enhance `java.math.BigInteger` constructors taking a `byte[]` argument by improving guarantees of internal invariants.

Raffaello Giulietti has updated the pull request incrementally with one additional commit since the last revision:

  Static Random instance.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16449/files
  - new: https://git.openjdk.org/jdk/pull/16449/files/4fcd905d..af2e4158

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16449&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16449&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16449.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16449/head:pull/16449

PR: https://git.openjdk.org/jdk/pull/16449