RFR: 8331907: BigInteger and BigDecimal should use optimized division [v2]

[Daniel Jeliński]

> Replace the custom unsigned divide / remainder functions with the compiler-optimized Long.divideUnsigned / remainderUnsigned.
> 
> No new tests. Existing tier1-3 tests continue to pass.
> 
> I added a new set of divide benchmarks. Results in thread.
> 
> I also removed the BigDecimal.toString benchmarks. They no longer serve their purpose - toString caches the returned value, so we were only benchmarking the cache access time.

Daniel Jeliński has updated the pull request incrementally with one additional commit since the last revision:

  Inline variable declaration

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Changes:
  - all: https://git.openjdk.org/jdk/pull/19134/files
  - new: https://git.openjdk.org/jdk/pull/19134/files/e565e1b6..a3fbc07d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19134&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19134&range=00-01

  Stats: 5 lines in 1 file changed: 0 ins; 2 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/19134.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19134/head:pull/19134

PR: https://git.openjdk.org/jdk/pull/19134