feat: build golang tests with codspeed instrumentation

[not-matthias]

The process is split into multiple parts:

• Discovery: Finds all the test packages for a project, filters out packages without benchmarks.
  • Verifier: Walks the AST of a source file to ensure the t *testing.B parameter isn't passed to a function.
• Templater: Copies the project to a tmp folder, creates a new cli/runner.go main file with the benchmarks.
  • Patcher: Patches the imports from testing to our codspeed compat package
• Runner: Builds the cli/runner.go and outputs the binary.

[codspeed-hq]

CodSpeed Performance Report

Congrats! CodSpeed is installed 🎉

🆕 11 new benchmarks were detected.

You will start to see performance impacts in the reports once the benchmarks are run from your default branch.

Detected benchmarks

• BenchmarkFibonacci20_Loop (68.6 µs)
• BenchmarkFibonacci20_bN (69.9 µs)
• BenchmarkSleep100ns (226 ns)
• BenchmarkSleep100us (100.1 µs)
• BenchmarkSleep10ms (10 ms)
• BenchmarkSleep10us (10.1 µs)
• BenchmarkSleep1ms (1 ms)
• BenchmarkSleep1us (1.1 µs)
• BenchmarkSleep50ms (50 ms)
• fibonacci(10) (557 ns)
• fibonacci(30) (8.7 ms)

[Copilot]

Pull Request Overview

This PR introduces comprehensive support for building and running Golang benchmarks with CodSpeed instrumentation. The implementation includes benchmark discovery, Go source patching, template generation, and walltime results collection for performance measurement integration.

Key Changes

• Implements a Rust-based Go benchmark runner with build and run commands
• Adds benchmark discovery and verification for Go test packages
• Creates source patching to replace standard testing imports with CodSpeed compatibility layer

Reviewed Changes

Copilot reviewed 51 out of 55 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
go-runner/src/*.rs	Core Rust implementation for Go benchmark runner with discovery, templating, and results collection
go-runner/testdata/*	Test data files including benchmark samples, raw results, and project submodules
example/*	Example Go project with benchmark tests and module configuration
.github/workflows/ci.yml	CI pipeline configuration for testing and integration
.gitmodules	Git submodule configuration for test projects