Benchmark: Dispose benchmark MemoryStreams to reduce GC noise #33
Description
Current: Benchmarks allocate MemoryStream per iteration (CompileVbaProjectBenchmark output, CompileMacroBenchmark macro stream) without cleanup, increasing GC pressure across iterations.
Proposed: Track the streams as fields and dispose them in [IterationCleanup], or return byte[]/length instead. Keep MemoryDiagnoser on to verify reduced allocation/GC noise.