Move benchmarks from main typeberry repository

[coderabbitai]

Context

As discussed in FluffyLabs/typeberry#690 (comment), we should move the benchmarks from the main typeberry repository to this testing repository.

Motivation

• Separates testing/benchmarking dependencies from the main codebase
• Allows keeping benchmark-specific dependencies (e.g., blake2b for comparison) without adding them to the main repository
• Cleaner separation of concerns

Tasks

• Move benchmark files from benchmarks/ directory in typeberry
• Set up benchmark infrastructure in typeberry-testing
• Update CI/CD to run benchmarks from the new location
• Document how to run benchmarks in the new repository

References

• PR: Use blake2b from hash-wasm typeberry#690
• Discussion: Use blake2b from hash-wasm typeberry#690 (comment)
• Requested by: @tomusdrw