implement runtime utility function to aid the benchmarking

[radkomih]

depends on gossamer bench-instance branch

• Benchmark_run exported function
• build with a tag benchmarks
  • remove the export when building without the tag (related configurable function exports #331)
• benchmarking api module
• pass a BenchmarkConfig containing the extrinsic, origin, repeat count
• reset the setup state for each iteration via rollback (DbWipe, DbCommit do nothing since the state implementation in Gossamer does not implement caching and nested transactions)
• whitelist known storage keys and signer key
• set the block number
• repeat and measure the average time
• track the db reads/writes
• return a BenchmarkResult containing the extrinsic time, db reads/writes
• add timestamp.set benchmark test
  • setup inputs/state
  • validate result/state
  • report metrics
  • switch to Gosemble's extrinsic type
• add more steps or implement components