feat(cli): Implement address flag for boundary targets create/update

This commit adds CLI support for addresses to be attached directly to a
Target, for all current types of Target (ssh and tcp).

It also clarifies the relevant documentation regarding the autogen of
API option functionality.

internal/proto/controller/api/resources/targets/v1/target.proto

@@ -211,6 +211,9 @@ message Target {
   // Output only. The available actions on this resource for this user.
   repeated string authorized_actions = 300 [json_name = "authorized_actions"]; // @gotags: `class:"public"`
 
+  // Optionally, a valid network address to connect to for this target. Can not be used alongside host sources.
+  string address = 540 [(custom_options.v1.generate_sdk_option) = true]; // @gotags: `class:"public"`
+
   // Deprecated fields
   reserved "application_credential_library_ids", "application_credential_libraries";
   reserved 150, 180;