Add FastBigDecimalParser support

[pjfanning]

Similar to the FastDoubleParser support added in Jackson 2.14. FastBigDecimalParser would be enabled optionally.
I have some code based on https://github.com/plokhotnyuk/jsoniter-scala

https://github.com/pjfanning/jackson-number-parse-bench/blob/main/src/main/java/org/example/jackson/bench/FastBigDecimalParser.java

Maybe something for Jackson 2.15.

Relates to #814 and #815

The current benchmark for FastBigDecimalParser suggests it is better for numbers with lots of digits (and still a little better for numbers with a small number of digits).

For BigInteger parsing, I got:

Benchmark                                 Mode  Cnt       Score       Error  Units
BigIntegerParserBench.bigDec1000         thrpt    5   35195.566 ±  2758.478  ops/s
BigIntegerParserBench.bigDec10000        thrpt    5    1232.178 ±   221.485  ops/s
BigIntegerParserBench.bigDec1000000      thrpt    5       0.396 ±     0.031  ops/s
BigIntegerParserBench.bigInt1000         thrpt    5   48308.680 ±   671.193  ops/s
BigIntegerParserBench.bigInt10000        thrpt    5     617.721 ±    14.032  ops/s
BigIntegerParserBench.bigInt1000000      thrpt    5       0.063 ±     0.002  ops/s
BigIntegerParserBench.fastBigDec1000     thrpt    5  138409.766 ± 10781.948  ops/s
BigIntegerParserBench.fastBigDec1000000  thrpt    5       2.342 ±     0.019  ops/s

[pjfanning]

A duplicate of #813