RFR: 8285001: Simplify StringLatin1.regionMatches [v2]

[Claes Redestad]

> There is no pair of character values in the latin1 range (0-255) that will make the condition at line 401 in `StringLatin1.java` true, so this test can be removed.
> 
> Added a test and a microbenchmark (which as expected sees a few ns/op improvement from this change). Took the opportunity to tune the default settings for the micro to reduce runtime from 30+ minutes to 3 with no discernible degradation of quality.

Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:

  Copyright

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8292/files
  - new: https://git.openjdk.java.net/jdk/pull/8292/files/a8894f79..434a0fd2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8292&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8292&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8292.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8292/head:pull/8292

PR: https://git.openjdk.java.net/jdk/pull/8292