perf: improve performance of bytea string decoding

[bokken]

improve the parsing of bytea hex encoded string by making a lookup table
for each of the valid ascii code points to the 4 bit numeric value

This is inspired by #2232

The length in this jmh bench mark is length of the hex string, so resulting byte[] is half that length.
At small sizes, there is very little difference, but as the sizes get larger, the differences are substantial.

Benchmark             (length)  Mode  Cnt        Score        Error  Units
ByteaParser.parse           24  avgt    5       26.764 ±      0.424  ns/op
ByteaParser.parse          216  avgt    5      198.609 ±      1.070  ns/op
ByteaParser.parse         9872  avgt    5    36716.658 ±   1439.702  ns/op
ByteaParser.parse       198724  avgt    5  1075320.427 ± 123970.425  ns/op
ByteaParser.parseLUT        24  avgt    5       31.374 ±      2.441  ns/op
ByteaParser.parseLUT       216  avgt    5      179.361 ±      0.455  ns/op
ByteaParser.parseLUT      9872  avgt    5     8898.861 ±    117.963  ns/op
ByteaParser.parseLUT    198724  avgt    5   127577.077 ±   4428.223  ns/op

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