Add RPC daemon using Silkworm

[canepat]

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)

[AskAlexSharov]

maybe you did mean:

go func() {
    select {
    case <-ctx.Done():  // it's just a Ctrl+C listener
       s.silkworm.StopRpcDaemon()
    }
}{}
s.silkworm.StartRpcDaemon()

?

[canepat]

I did it that way because the existing cli.StartRpcServer call blocks the calling goroutine and StartRpcDaemon does not, so I replicated the same behaviour; in other words, StartRpcServer calls startRegularRpcServer, which uses a pattern similar to mine (i.e. defer + <- ctx.Done()).

[AskAlexSharov]

Yes, and if it blocks - then only way to get to this line of code - “exit without error” - which means server already don’t need shutdown.

In my head “StopRpcDaemon” can gracefuly stop working server. We need call it at “Ctrl+C”

[canepat]

OK, now I see it, I changed the code

[AskAlexSharov]

ah, ok. can add it to name like "StartInBackground" - because most of go's funcs are blocking.