Optimize z_stream internal buffer allocations

[zargovv]

This pull request gets rid of "Probably not enough output buffer was allocated" error and redundant allocations of zlib internal buffers.

The idea is to minimize redundant (de-)allocation amount of the zlib internal buffers. Although the madler zlib claims to be thread-safe as long as the allocator passed as zalloc is, this commit carries a thread local static z_stream. It also requires us to manually end the stream: function deflate_end introduced.
Reference: zlib manual

In fact, this optimization can be pushed just a bit further. Currently, deflate stream is reinitialized on every klass_predictor_predict call, but could be initialized once per every thread.

Additionally, I wanted to check some SIMD-accelerated implementations of ZLIB, which includes: zlib-chromium, zlib-ng, zlib-cloudflare and [!]zlib-intel.

Mentioned repos are under the zlib license.

Also it would be nice to check out libdeflate. It doesn't include gzip headers, nor checksums and claimed to be ~33% faster than zlib-cloudflare by some benchmarks (Haven't tested myself though).

All benchmarks below were intentionally tested on a single thread.
Every library from the list have been compiled using the default branch.
Benchmarks using ag-news dataset: ./nob; ./build/knn ./data/ag-news/classes.csv ./data/ag-news/test.csv
CPU: i7-12700F, 2100 Mhz
RAM: 32GB DDR5-5200 MT/s XMP 3.0
HDD: Seq 64 127 MB/s

Commit 52e1d9e:

Success rate: 79/100 (0.790000)
Total Elapsed: 271.484s
Avg Elapsed: 2.71484

z_stream optimization (from now on will be referred to as "zs opt"):

Success rate: 79/100 (0.790000)
Total Elapsed: 264.248s
Avg Elapsed: 2.64248s

zs opt + zlib-ng

Success rate: 79/100 (0.790000)
Total Elapsed: 282.062s
Avg Elapsed: 2.82062s

zs opt + zlib-chromium:

Success rate: 79/100 (0.790000)
Total Elapsed: 263.481s
Avg Elapsed: 2.63481s

zs opt + zlib-intel:

Success rate: 79/100 (0.790000)
Total Elapsed: 261.152s
Avg Elapsed: 2.61152s

zs opt + zlib-cloudflare:

Success rate: 78/100 (0.780000)
Total Elapsed: 224.895s
Avg Elapsed: 2.24895s

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Open for discussions

P.S.
After some research, libdeflate seems to work well: Success rate has increased to 82% for the same dataset, avg elapsed time decreased to 1.96734s (Tested with K = 2 and compression level set to 9). In the end the speed has risen by ~28% compared to the original deflate_sv.
The increase in the success rate makes sense, since zlib and gzip headers are putting some format-specific headers, which potentially might add inaccuracy to the classification.