KAFKA-20249: Optimize raw value extraction in headers-aware deserializers

[zheguang]

This patch implements two optimizations, and their JMH benchmarks.

1. Skipping
   Previously the raw value extraction in headers-aware deserializers undergoes deserialization and/or copying of headers, while only skipping is required. This happens for both empty and nonempty headers.

2. Empty headers copying
   Empty headers have constant metadata footprint: the headers size is varint-encoded 1 byte of 0, and headers themselves consume no bytes. Based on this invariant, the ByteBuffer-based extraction can be replaced with a direct System.arraycopy, which is a Java native method optimized for specific platforms.

Benchmark:
This patch also includes JMH benchmarks to test the speedup. On my local machine, Optimization 1 speedup is 2-6x speedup. Optimization 2 is 1.35x.

Below is the throughput comparison of a recorded JMH run:

Benchmark                                                Mode  Cnt      Score     Error  Units
RawBytesExtraction.testRawAggregationWithHeaders        thrpt   15   1481.854 ±  31.448  ops/s
RawBytesExtraction.testRawAggregationWithHeadersOpt     thrpt   15  11797.165 ± 103.432  ops/s

RawBytesExtraction.testRawAggregationWithoutHeaders     thrpt   15   8359.080 ±  47.918  ops/s
RawBytesExtraction.testRawAggregationWithoutHeadersOpt  thrpt   15  15298.827 ± 452.741  ops/s

RawBytesExtraction.testRawValueWithoutHeaders           thrpt   15  11329.997 ± 260.399  ops/s
RawBytesExtraction.testRawValueWithoutHeadersOpt        thrpt   15  15372.816 ± 184.651  ops/s

Test:

• Existing unit test covering nonempty headers
• Added test case for empty headers