This introduces _experimental_ RPC daemon run by embedded Silkworm
library. Same notes as in PR #8353 apply here plus the following ones:
- activated if `http` command-line option is enabled and `silkworm.path`
option is present, nothing more is required (i.e. currently, both block
execution and RPC daemon run by Silkworm when specifying
`silkworm.path`, just to keep things as simple as possible)
- only Execution API endpoints are implemented by Silkworm RPCDaemon,
whilst Engine API endpoints are still served by Erigon RPCDaemon
- some features are still missing, in particular:
- state change notification handling
- custom JSON RPC settings (i.e. Erigon RPC settings are not passed to
Silkworm yet)
