Add reproducible BenchmarkDotNet suite

[thomhurst]

Summary

• add a BenchmarkDotNet 0.15.8 project with seven processor scenarios
• measure completed-task and Task.Yield selectors at 1k, 10k, and 100k items with memory diagnostics
• document full runs, filtering, and cross-revision artifact comparison
• keep the benchmark executable out of release package discovery

Validation

• full Release solution build succeeds
• 1,611 tests pass across net8.0, net9.0, and net10.0
• BenchmarkSwitcher discovers all seven scenarios
• Dry-job smoke executes all unbounded combinations across both workloads and all sizes

Closes #339

[greptile-apps]

Greptile Summary

This PR adds a reproducible BenchmarkDotNet suite for the async processor. The main changes are:

• Seven processor scenarios across two workloads and three input sizes.
• Benchmark run, filtering, and revision-comparison guidance.
• Solution and pipeline integration for benchmark builds.
• Benchmark exclusion from release package discovery.

Confidence Score: 5/5

This looks safe to merge.

• The pipeline now builds the benchmark project before packaging.
• Benchmark build failures stop the workflow.
• No blocking issues remain in the updated code.

Important Files Changed

Filename	Overview
EnumerableAsyncProcessor.Pipeline/Modules/BuildBenchmarkProjectsModule.cs	Adds explicit Release builds for benchmark projects and propagates build failures.
EnumerableAsyncProcessor.Pipeline/Modules/PackProjectsModule.cs	Makes packaging depend on the benchmark build while excluding benchmarks from package discovery.
EnumerableAsyncProcessor.Pipeline/Program.cs	Registers benchmark validation for pipeline runs.
TomLonghurst.EnumerableAsyncProcessor.sln	Adds the benchmark project to Debug and Release solution builds.
benchmarks/EnumerableAsyncProcessor.Benchmarks.csproj	Defines a non-packable .NET 10 BenchmarkDotNet executable.
benchmarks/ProcessorBenchmarks.cs	Defines the benchmark scenarios, workloads, input sizes, and memory diagnostics.

_{Reviews (2): Last reviewed commit: "ci: build benchmarks in pipeline (#353)" | Re-trigger Greptile}