RFR: 8303401: Add a Vector API equalsIgnoreCase micro benchmark [v4]

[Eirik Bjorsnos]

> This PR suggests we add a vectorized equalsIgnoreCase benchmark to the set of benchmarks in `org.openjdk.bench.jdk.incubator.vector`. This benchmark serves as an example of how vectorization can be useful also in the area of text processing. It takes advantage of the fact that ASCII and Latin-1 were designed to optimize case-twiddling operations.
> 
> The code came about during the work on #12632, where vectorization was deemed out of scope.
> 
> Benchmark results:
> 
> 
> Benchmark                             (size)  Mode  Cnt     Score   Error  Units
> EqualsIgnoreCaseBenchmark.scalar          16  avgt   15    20.671 ± 0.718  ns/op
> EqualsIgnoreCaseBenchmark.scalar          32  avgt   15    46.155 ± 3.258  ns/op
> EqualsIgnoreCaseBenchmark.scalar          64  avgt   15    68.248 ± 1.767  ns/op
> EqualsIgnoreCaseBenchmark.scalar         128  avgt   15   148.948 ± 0.890  ns/op
> EqualsIgnoreCaseBenchmark.scalar        1024  avgt   15  1090.708 ± 7.540  ns/op
> EqualsIgnoreCaseBenchmark.vectorized      16  avgt   15    21.872 ± 0.232  ns/op
> EqualsIgnoreCaseBenchmark.vectorized      32  avgt   15    11.378 ± 0.097  ns/op
> EqualsIgnoreCaseBenchmark.vectorized      64  avgt   15    13.703 ± 0.135  ns/op
> EqualsIgnoreCaseBenchmark.vectorized     128  avgt   15    21.632 ± 0.735  ns/op
> EqualsIgnoreCaseBenchmark.vectorized    1024  avgt   15   105.509 ± 7.493  ns/op

Eirik Bjorsnos has updated the pull request incrementally with two additional commits since the last revision:

 - Adjust whitespace as suggested in review
 - Replace Blackhold.consume with return values

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/12790/files
  - new: https://git.openjdk.org/jdk/pull/12790/files/6bc04db0..00253baa

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12790&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12790&range=02-03

  Stats: 7 lines in 1 file changed: 1 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/12790.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12790/head:pull/12790

PR: https://git.openjdk.org/jdk/pull/12790