pw_rpc: Disable client stream end callback by default

- Supporting a client stream end callback requires ServerReader/Writer
  object to store a pw::Function, which may be a significant overhead.
  Many applications may not need this callback, so the callback optional
  and disable it by default.
- Fail with a helpful static_assert if set_on_client_stream_end() is
  called when that callback is disabled.

Change-Id: I4b27e162953534aaa024aaca9e84b12570605fc9
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/51527
Reviewed-by: Alexei Frolov <frolv@google.com>
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pw_rpc/BUILD.gn b/pw_rpc/BUILD.gn
index dac6ea8..42f04c4 100644
--- a/pw_rpc/BUILD.gn
+++ b/pw_rpc/BUILD.gn
@@ -46,7 +46,10 @@
 
 pw_source_set("server") {
   public_configs = [ ":public_include_path" ]
-  public_deps = [ ":common" ]
+  public_deps = [
+    ":common",
+    ":config",
+  ]
   deps = [ dir_pw_log ]
   public = [
     "public/pw_rpc/server.h",