rego: Add comprehensive WASM performance benchmarks (#7841)

Added WASM vs topdown comparative benchmarks to track performance
regressions mentioned in issue #7759. The benchmarks provide visibility
into compilation overhead, cold start penalties, and memory reporting.

Added 4 critical benchmarks:
- BenchmarkWASMCompilationTargets: Compilation overhead metrics
- BenchmarkWASMColdStartTargets: Cold start penalty analysis
- BenchmarkMemoryAllocationTargets: Memory usage comparison with CGO warning
- BenchmarkBundleSizeTargets: Policy size scaling impacts

The memory benchmarks include a note about CGO allocation tracking
limitations when using wasmtime-go.

Signed-off-by: Anivar Aravind <[email protected]>
Signed-off-by: Anivar A Aravind <[email protected]>
Signed-off-by: Anivar A Aravind <[email protected]>

Author: anivar