consider using sync.Pool for heavy allocations

[nkryuchkov]

Is your feature request related to a problem? Please describe.
Some parts of code like message validation or non-committee observer allocate a lot of memory

Describe the solution you'd like
Analyze if we could use sync.Pool to reuse the same memory and reduce the amount of allocations. Implement it if so.

Additional context
Use Pyroscope to find where we need to apply it first