feat: add minimal unopinionated reqresp v1 package

[samcm]

Summary

• Adds a new minimal, unopinionated request/response package in pkg/consensus/mimicry/p2p/reqresp/v1
• Supports both single-response and chunked-response protocols
• Uses Go generics for type safety without imposing specific encoding formats
• No external dependencies on Prysm or ZRNT types

Key Features

• Generic interfaces: Core abstractions use generics for compile-time type safety
• Chunked protocol support: Enables protocols that send multiple response chunks (needed for BeaconBlocksByRangeV2)
• Pluggable encoding: Users provide their own encoder implementation (JSON, SSZ, protobuf, etc.)
• Optional compression: Compression is optional and pluggable
• Clean separation: Handler logic, client logic, and service management are clearly separated

Implementation Details

The package includes:

• interface.go: Core interfaces and abstractions
• types.go: Basic types, error definitions, and configuration structs
• handler.go: Generic handler implementation with request/response processing
• chunked_handler.go: Support for protocols that send multiple response chunks
• client.go: Client implementation with retry logic and chunked response support
• reqresp.go: Main service implementation that ties everything together
• protocols.go: Helper types for creating protocols
• example_test.go: Usage examples showing JSON encoding, custom protocols, and chunked responses

Test Plan

• Package compiles successfully
• Examples demonstrate proper usage
• No go vet issues
• Unit tests to be added in follow-up PR (targeting >70% coverage)

🤖 Generated with Claude Code

[codecov]

Codecov Report

Attention: Patch coverage is 0.90909% with 327 lines in your changes missing coverage. Please review.

Project coverage is 39.47%. Comparing base (1583744) to head (99071a5).
Report is 8 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/consensus/mimicry/p2p/reqresp/v1/reqresp.go	0.00%	189 Missing ⚠️
.../consensus/mimicry/p2p/reqresp/v1/eth/protocols.go	0.00%	77 Missing ⚠️
...ensus/mimicry/p2p/reqresp/v1/ssz_snappy_encoder.go	0.00%	30 Missing ⚠️
pkg/consensus/mimicry/p2p/reqresp/v1/protocols.go	0.00%	26 Missing ⚠️
pkg/consensus/mimicry/crawler/crawler.go	37.50%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #66      +/-   ##
==========================================
+ Coverage   39.43%   39.47%   +0.04%     
==========================================
  Files          59       63       +4     
  Lines        5942     6275     +333     
==========================================
+ Hits         2343     2477     +134     
- Misses       3354     3529     +175     
- Partials      245      269      +24     

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