INIT: Add --binary flag to chain serve

[Pantani]

Add the ability to specify a binary to run the chain serve command instead of building the source. Using this flag, you can set a chain binary, and the command will not build the proto buffers and the binary from the source, only init the chain based on the config file and run.

[julienrbrt]

I would prefer instead of the binary that it just looks up in the go bin path for the actual built binary.
Feels weird to be able to run any binary imho. Ignite is opinionated, so let's stay that way for a better UX.