confighttp: embed confignet.AddrConfig in confighttp.ServerConfig

[axw]

See #14058 (comment)

I would like to make confighttp.ServerConfig and configgrpc.ServerConfig more consistent by embedding confignet.AddrConfig in the confighttp struct like we do in configgrpc.

i.e. remove this:

opentelemetry-collector/config/confighttp/server.go

Lines 34 to 36 in f498a89

	type ServerConfig struct {
	// Endpoint configures the listening address for the server.
	Endpoint string `mapstructure:"endpoint,omitempty"`

and add something equivalent to this:

opentelemetry-collector/config/configgrpc/configgrpc.go

Lines 174 to 176 in f498a89

	type ServerConfig struct {
	// Server net.Addr config. For transport only "tcp" and "unix" are valid options.
	NetAddr confignet.AddrConfig `mapstructure:",squash"`

By doing this, we would have a more natural place to add things like #14058 which should be common to both gRPC and HTTP servers. It would also enable HTTP servers to bind to Unix domain sockets: #8752

This would be a breaking API change, so should be done before #9380.

[atoulme]

Careful that AddrConfig also has a DialerConfig which might be a bit weird for a server endpoint. Not sure about the Transport field as well.

[axw]

@atoulme good point, maybe AddrConfig should be split into client & server configs too - I would keep that as a separate effort though. Transport is relevant, that's how we would support unix domain sockets.

[atoulme]

Unfortunately, confignet is stable.