Add the ability to profile the benchmarks w/ a flamegraph feature (#183)

* feat: Integrate flamegraph profiling in benchmarks

- Introduce "flamegraph" feature flag for optional profiling integration
- Add benchmark profiling support in `compressed_snark` and `recursive_snark` groups
- Update Cargo.toml with `pprof` and `cfg-if` dependencies

* ci: Build benches to make sure they don't bit-rot

- Integrate bench build step into GitHub Actions workflow

.github/workflows/rust.yml

@@ -25,6 +25,8 @@ jobs:
       run: cargo build --target wasm32-unknown-unknown
     - name: Build examples
       run: cargo build --examples --verbose
+    - name: Build benches
+      run: cargo build --benches --verbose
     - name: Run tests
       run: cargo +stable test --release --verbose
     - name: Check Rustfmt Code Style