Faster parsing: reduce String usage, list-based input rows.

[gianm]

Three changes:

1. Reworked FastLineIterator to optionally avoid generating Strings
   entirely, and reduce copying somewhat. Benefits the line-oriented
   JSON, CSV, delimited (TSV), and regex formats.

2. In the delimited (TSV) format, when the delimiter is a single byte,
   split on UTF-8 bytes directly.

3. In CSV and delimited (TSV) formats, use list-based input rows when
   the column list is provided upfront by the user.

Benchmarks below. Findings:

• JsonLineReaderBenchmark only benefits from change (1), and got a 15% improvement.
• DelimitedInputFormatBenchmark with fromHeader: true benefits from (1) and (2), and got a 22% improvement.
• DelimitedInputFormatBenchmark with fromHeader: false benefits from all three changes, and got a 30% improvement.

Benchmark                               (fromHeader)  Mode  Cnt     Score    Error  Units
DelimitedInputFormatBenchmark.baseline         false  avgt    5  1912.257 ± 39.227  us/op [master]
DelimitedInputFormatBenchmark.baseline          true  avgt    5  1953.915 ± 44.787  us/op [master]
JsonLineReaderBenchmark.baseline                      avgt    5  2055.294 ± 28.688  us/op [master]

DelimitedInputFormatBenchmark.baseline         false  avgt    5  1321.142 ± 10.115  us/op [patch]
DelimitedInputFormatBenchmark.baseline          true  avgt    5  1506.412 ± 15.892  us/op [patch]
JsonLineReaderBenchmark.baseline                      avgt    5  1734.426 ± 38.518  us/op [patch]

[gianm]

The only failure is IncrementalIndexIngestionTest.testMultithreadAddFactsUsingExpressionAndJavaScript, which is flaky now, and fixed by #15697. (By removing the test, as it's testing something we don't need.)

[clintropolis]

👍