RFR: 8372353: API to compute the byte length of a String encoded in a given Charset

[Liam Miller-Cushon]

This implements an API to return the byte length of a String encoded in a given charset. See [JDK-8372353](https://bugs.openjdk.org/browse/JDK-8372353) for background.

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Benchmark                              (encoding)  (stringLength)   Mode  Cnt          Score          Error  Units
StringLoopJmhBenchmark.getBytes             ASCII              10  thrpt    5  406782650.595 ± 16960032.852  ops/s
StringLoopJmhBenchmark.getBytes             ASCII             100  thrpt    5  172936926.189 ±  4532029.201  ops/s
StringLoopJmhBenchmark.getBytes             ASCII            1000  thrpt    5   38830681.232 ±  2413274.766  ops/s
StringLoopJmhBenchmark.getBytes             ASCII          100000  thrpt    5     458881.155 ±    12818.317  ops/s
StringLoopJmhBenchmark.getBytes            LATIN1              10  thrpt    5   37193762.990 ±  3962947.391  ops/s
StringLoopJmhBenchmark.getBytes            LATIN1             100  thrpt    5   55400876.236 ±  1267331.434  ops/s
StringLoopJmhBenchmark.getBytes            LATIN1            1000  thrpt    5   11104514.001 ±    41718.545  ops/s
StringLoopJmhBenchmark.getBytes            LATIN1          100000  thrpt    5     182535.414 ±    10296.120  ops/s
StringLoopJmhBenchmark.getBytes             UTF16              10  thrpt    5  113474681.457 ±  8326589.199  ops/s
StringLoopJmhBenchmark.getBytes             UTF16             100  thrpt    5   37854103.127 ±  4808526.773  ops/s
StringLoopJmhBenchmark.getBytes             UTF16            1000  thrpt    5    4139833.009 ±    70636.784  ops/s
StringLoopJmhBenchmark.getBytes             UTF16          100000  thrpt    5      57644.637 ±     1887.112  ops/s
StringLoopJmhBenchmark.getBytesLength       ASCII              10  thrpt    5  946701647.247 ± 76938927.141  ops/s
StringLoopJmhBenchmark.getBytesLength       ASCII             100  thrpt    5  396615374.479 ± 15167234.884  ops/s
StringLoopJmhBenchmark.getBytesLength       ASCII            1000  thrpt    5  100464784.979 ±   794027.897  ops/s
StringLoopJmhBenchmark.getBytesLength       ASCII          100000  thrpt    5    1215487.689 ±     1916.468  ops/s
StringLoopJmhBenchmark.getBytesLength      LATIN1              10  thrpt    5  221265102.323 ± 17013983.056  ops/s
StringLoopJmhBenchmark.getBytesLength      LATIN1             100  thrpt    5  137617873.887 ±  5842185.781  ops/s
StringLoopJmhBenchmark.getBytesLength      LATIN1            1000  thrpt    5   92540259.130 ±  3839233.582  ops/s
StringLoopJmhBenchmark.getBytesLength      LATIN1          100000  thrpt    5    1136360.285 ±   426475.121  ops/s
StringLoopJmhBenchmark.getBytesLength       UTF16              10  thrpt    5  329508584.830 ±  6277534.933  ops/s
StringLoopJmhBenchmark.getBytesLength       UTF16             100  thrpt    5   86396600.366 ±  4287569.267  ops/s
StringLoopJmhBenchmark.getBytesLength       UTF16            1000  thrpt    5   10037994.564 ±   779239.446  ops/s
StringLoopJmhBenchmark.getBytesLength       UTF16          100000  thrpt    5      99218.929 ±     2854.843  ops/s
StringLoopJmhBenchmark.utf8LenByLoop        ASCII              10  thrpt    5  409066999.717 ± 25444799.130  ops/s
StringLoopJmhBenchmark.utf8LenByLoop        ASCII             100  thrpt    5   72126088.461 ± 42992009.452  ops/s
StringLoopJmhBenchmark.utf8LenByLoop        ASCII            1000  thrpt    5    8300806.448 ±   533912.423  ops/s
StringLoopJmhBenchmark.utf8LenByLoop        ASCII          100000  thrpt    5      87356.021 ±     7863.743  ops/s
StringLoopJmhBenchmark.utf8LenByLoop       LATIN1              10  thrpt    5  356802960.574 ± 24814016.238  ops/s
StringLoopJmhBenchmark.utf8LenByLoop       LATIN1             100  thrpt    5   85043539.617 ± 30538310.706  ops/s
StringLoopJmhBenchmark.utf8LenByLoop       LATIN1            1000  thrpt    5    9952675.100 ±  2922230.486  ops/s
StringLoopJmhBenchmark.utf8LenByLoop       LATIN1          100000  thrpt    5      79410.881 ±    50777.786  ops/s
StringLoopJmhBenchmark.utf8LenByLoop        UTF16              10  thrpt    5  304196311.102 ± 20381571.060  ops/s
StringLoopJmhBenchmark.utf8LenByLoop        UTF16             100  thrpt    5   84223829.681 ± 10787815.139  ops/s
StringLoopJmhBenchmark.utf8LenByLoop        UTF16            1000  thrpt    5   11046224.275 ±  1200731.406  ops/s
StringLoopJmhBenchmark.utf8LenByLoop        UTF16          100000  thrpt    5     112590.802 ±     3741.019  ops/s

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Commit messages:
 - Whitespace
 - Apply suggestions from code review
 - 8372353: API to compute the byte length of a String encoded in a given Charset

Changes: https://git.openjdk.org/jdk/pull/28454/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28454&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8372353
  Stats: 213 lines in 4 files changed: 213 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/28454.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28454/head:pull/28454

PR: https://git.openjdk.org/jdk/pull/28454