perf(col_str): Reduce heap allocations

[mauidude]

Summary

Reducing the amount of allocations, mostly around ColStr and Buffer.

git checkout main
go test -benchmem -run=^$ -bench ^BenchmarkColStr_DecodeColumn$ github.com/ClickHouse/ch-go/proto -race -count=25 > old.txt

git checkout reduce-allocations
go test -benchmem -run=^$ -bench ^BenchmarkColStr_DecodeColumn$ github.com/ClickHouse/ch-go/proto -race -count=25 > new.txt

go install golang.org/x/perf/cmd/benchstat@latest

benchstat old.txt new.txt
goos: darwin
goarch: arm64
pkg: github.com/ClickHouse/ch-go/proto
cpu: Apple M4 Max
                       │   old.txt   │               new.txt               │
                       │   sec/op    │   sec/op     vs base                │
ColStr_DecodeColumn-16   443.4µ ± 1%   376.3µ ± 0%  -15.13% (p=0.000 n=25)

                       │   old.txt    │               new.txt                │
                       │     B/s      │     B/s       vs base                │
ColStr_DecodeColumn-16   70.98Mi ± 1%   83.63Mi ± 0%  +17.82% (p=0.000 n=25)

                       │   old.txt    │               new.txt                │
                       │     B/op     │    B/op      vs base                 │
ColStr_DecodeColumn-16   15.62Ki ± 0%   0.00Ki ± 0%  -100.00% (p=0.000 n=25)

                       │   old.txt   │               new.txt                │
                       │  allocs/op  │  allocs/op   vs base                 │
ColStr_DecodeColumn-16   1.000k ± 0%   0.000k ± 0%  -100.00% (p=0.000 n=25)

Checklist

Delete items not relevant to your PR:

• A human-readable description of the changes was provided to include in CHANGELOG

[SpencerTorres]

Excellent 👌