Unify gRPC settings for server connections

[ccaraman]

Is your feature request related to a problem? Please describe.
Both Opencensus Receiver and Otlp Receiver have similar gRPC Server settings

opentelemetry-collector/receiver/opencensusreceiver/config.go

Lines 28 to 48 in a637b41

	type Config struct {
	receiver.SecureReceiverSettings `mapstructure:",squash"` // squash ensures fields are correctly decoded in embedded struct
	// Transport to use: one of tcp or unix, defaults to tcp
	Transport string `mapstructure:"transport"`
	// CorsOrigins are the allowed CORS origins for HTTP/JSON requests to grpc-gateway adapter
	// for the OpenCensus receiver. See github.com/rs/cors
	// An empty list means that CORS is not enabled at all. A wildcard (*) can be
	// used to match any origin or one or more characters of an origin.
	CorsOrigins []string `mapstructure:"cors_allowed_origins"`
	// Keepalive anchor for all the settings related to keepalive.
	Keepalive *serverParametersAndEnforcementPolicy `mapstructure:"keepalive,omitempty"`
	// MaxRecvMsgSizeMiB sets the maximum size (in MiB) of messages accepted by the server.
	MaxRecvMsgSizeMiB uint64 `mapstructure:"max_recv_msg_size_mib,omitempty"`
	// MaxConcurrentStreams sets the limit on the number of concurrent streams to each ServerTransport.
	MaxConcurrentStreams uint32 `mapstructure:"max_concurrent_streams,omitempty"`
	}

and

opentelemetry-collector/receiver/otlpreceiver/config.go

Lines 27 to 49 in a637b41

	// Config defines configuration for OTLP receiver.
	type Config struct {
	receiver.SecureReceiverSettings `mapstructure:",squash"` // squash ensures fields are correctly decoded in embedded struct
	// Transport to use: one of tcp or unix, defaults to tcp
	Transport string `mapstructure:"transport"`
	// CorsOrigins are the allowed CORS origins for HTTP/JSON requests to grpc-gateway adapter
	// for the OTLP receiver. See github.com/rs/cors
	// An empty list means that CORS is not enabled at all. A wildcard (*) can be
	// used to match any origin or one or more characters of an origin.
	CorsOrigins []string `mapstructure:"cors_allowed_origins"`
	// Keepalive anchor for all the settings related to keepalive.
	Keepalive *serverParametersAndEnforcementPolicy `mapstructure:"keepalive,omitempty"`
	// MaxRecvMsgSizeMiB sets the maximum size (in MiB) of messages accepted by the server.
	MaxRecvMsgSizeMiB uint64 `mapstructure:"max_recv_msg_size_mib,omitempty"`
	// MaxConcurrentStreams sets the limit on the number of concurrent streams to each ServerTransport.
	// TODO(nilebox): This setting affecting HTTP/2 streams need to be tested
	MaxConcurrentStreams uint32 `mapstructure:"max_concurrent_streams,omitempty"`
	}

These should be extracted into a common gRPC Server Setting to reduce duplicate logic and have it exposed for other Server connections.

Describe the solution you'd like
A clear and concise description of what you want to happen.
Have a struct similar to GRPCSettings

opentelemetry-collector/config/configgrpc/configgrpc.go

Line 40 in a637b41

type GRPCSettings struct {

but for Server.

This would receiver the existing GRPCSettings to be renamed to GRPCClientSettings.

Additional context
This is just a cleanup.