feat(build): Add CodeGenBuilder (#1154)

This commit adds a new `CodeGenBuilder` that replaces the
client/server generate fn with a builder stlye that allows
adding config items in an non-breaking way. This also deprecates
both of the client/server generate fn in favor of the builder ones.

tonic-build/src/server.rs

@@ -10,12 +10,30 @@ use syn::{Ident, Lit, LitStr};
 ///
 /// This takes some `Service` and will generate a `TokenStream` that contains
 /// a public module containing the server service and handler trait.
+#[deprecated(since = "0.8.3", note = "Use CodeGenBuilder::generate_server")]
 pub fn generate<T: Service>(
     service: &T,
     emit_package: bool,
     proto_path: &str,
     compile_well_known_types: bool,
     attributes: &Attributes,
+) -> TokenStream {
+    generate_internal(
+        service,
+        emit_package,
+        proto_path,
+        compile_well_known_types,
+        attributes,
+        &HashSet::default(),
+    )
+}
+
+pub(crate) fn generate_internal<T: Service>(
+    service: &T,
+    emit_package: bool,
+    proto_path: &str,
+    compile_well_known_types: bool,
+    attributes: &Attributes,
     disable_comments: &HashSet<String>,
 ) -> TokenStream {
     let methods = generate_methods(service, proto_path, compile_well_known_types);