RFR: 8310813: Simplify and modernize equals, hashCode, and compareTo for BigInteger [v5]

[Pavel Rappo]

> Please review this PR to use modern APIs and language features to simplify equals, hashCode, and compareTo for BigInteger. If you have any performance concerns, please raise them.
> 
> This PR is cherry-picked from a bigger, not-yet-published PR, to test the waters. That latter PR will be published soon.

Pavel Rappo has updated the pull request incrementally with two additional commits since the last revision:

 - Group params coarser (suggested by @cl4es)
   
   - Splits 20 params into 3 groups: (S)mall, (M)edium and (L)arge.
     Every testXYZ method invokes M operations, where M is the maximum
     number of elements in a group. Shorter groups are cyclically padded.
   - Uses the org.openjdk.jmh.infra.Blackhole API and increases
     benchmark time.
   - Fixes a bug in Shared that precluded 0 from being in a pair.
 - Use better overloads (suggested by @cl4es)
   
   - Uses simpler, more suitable overloads for the subrange
     starting from 0

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/14630/files
  - new: https://git.openjdk.org/jdk/pull/14630/files/eb4b9775..5af2d5dc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14630&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14630&range=03-04

  Stats: 189 lines in 5 files changed: 75 ins; 86 del; 28 mod
  Patch: https://git.openjdk.org/jdk/pull/14630.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14630/head:pull/14630

PR: https://git.openjdk.org/jdk/pull/14630