Feat/enable non namespaces

[loocapro]

Hi @mattsse as agreed I am opening this PR in order to enable to start a reth node with empty http.api modules. This is required for any user who just wants to enable some custom RPC namespace.

[mattsse]

ty!

I believe this can be supported with two checks in rpc modulesecltion parser instead

check for none|None and is_empty

where is_empty is the first check on s

[loocapro]

ty!

I believe this can be supported with two checks in rpc modulesecltion parser instead

check for none|None and is_empty

where is_empty is the first check on s

Thanks @mattsse , everything seems to work. I am not too sure we require the s.is_empty()check as the cli args gets validated and i cannot seem to pass an empty --http.api.

[mattsse]

lgtm