Add and modernize Go hot-path benchmarks

[Uzer007-admin]

Summary

This PR expands and modernizes the Go benchmark coverage for Reindexer hot paths.

All changes are limited to benchmark files and do not modify the production API or runtime behavior.

Changes

• Migrate existing benchmarks from manual b.N loops to b.Loop().
• Add CJSON base64 benchmarks covering:
  • encoding and decoding payloads from 0 to 4096 bytes;
  • encoding and decoding a small real-world-shaped payload set;
  • payload size distribution, base64 padding classes, and size buckets.
• Add Serializer.PutValue microbenchmarks for:
  • integers;
  • strings;
  • slices.
• Add WhereExpressions query builder benchmarks for:
  • Field/Values;
  • FlatArrayLen/Now;
  • comparison with the legacy slice-based function serialization path.
• Modernize RPC encoder/decoder, network buffer, and serializer benchmarks.
• Modernize end-to-end Reindexer benchmarks for inserts, updates, deletes, CJSON, JSON, and Gob.
• Remove redundant ResetTimer calls where timing is already managed by b.Loop.
• Bound buffer growth in the writeIntBits benchmark to avoid allocations proportional to b.N.
• Make the delete/update ID range independent of the framework-selected b.N.
• Preserve commit-phase measurement in transaction benchmarks.

Scope

All changes are contained in _test.go benchmark files. There are no production code, public API, or runtime behavior changes.

[MadSchemas]

Do not think, that all those 'legacy' things should be in our benchmarks set. This measurements may be relevant for the specific PR, but not as a part of regular codebase