Reland "New build target p2p:stun_types"

This is a reland of 5b4fcb5bf69218c2f42ca2b0cada6c15f2f638e9

Original change's description:
> New build target p2p:stun_types
>
> The media:rtc_media_base target needs definitions of various
> stun-related types and constant. With this new smaller target, it no
> longer needs to depend on all of p2p.
>
> Bug: webrtc:8733
> Change-Id: I05910b6915f6d2c96e8f52a017adbc7eb693dca8
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/150945
> Commit-Queue: Niels Moller <nisse@webrtc.org>
> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
> Reviewed-by: Steve Anton <steveanton@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#29036}

Tbr: steveanton@webrtc.org
Bug: webrtc:8733
Change-Id: I1847007ecf29e0e6a27f559b92df632a1cd69280
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/151880
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29092}
diff --git a/p2p/BUILD.gn b/p2p/BUILD.gn
index bc80b75..1583cfb 100644
--- a/p2p/BUILD.gn
+++ b/p2p/BUILD.gn
@@ -15,9 +15,17 @@
   ]
 }
 
-# TODO(bugs.webrtc.org/8733): Move base/stun.{h,cc} into this target,
-# after downstream dependencies are updated.
 rtc_source_set("stun_types") {
+  sources = [
+    "base/stun.cc",
+    "base/stun.h",
+  ]
+  deps = [
+    "../rtc_base:checks",
+    "../rtc_base:rtc_base",
+    "../rtc_base:rtc_base_approved",
+    "//third_party/abseil-cpp/absl/memory",
+  ]
 }
 
 rtc_static_library("rtc_p2p") {
@@ -66,8 +74,6 @@
     "base/regathering_controller.h",
     "base/relay_port.cc",
     "base/relay_port.h",
-    "base/stun.cc",
-    "base/stun.h",
     "base/stun_port.cc",
     "base/stun_port.h",
     "base/stun_request.cc",
@@ -91,6 +97,7 @@
   ]
 
   deps = [
+    ":stun_types",
     "../api:libjingle_peerconnection_api",
     "../api:packet_socket_factory",
     "../api:scoped_refptr",
@@ -163,6 +170,7 @@
       ":fake_port_allocator",
       ":p2p_server_utils",
       ":rtc_p2p",
+      ":stun_types",
       "../api:libjingle_peerconnection_api",
       "../api:packet_socket_factory",
       "../rtc_base",
@@ -209,6 +217,7 @@
       ":p2p_server_utils",
       ":p2p_test_utils",
       ":rtc_p2p",
+      ":stun_types",
       "../api:libjingle_peerconnection_api",
       "../api:scoped_refptr",
       "../api/units:time_delta",
@@ -242,6 +251,7 @@
   ]
   deps = [
     ":rtc_p2p",
+    ":stun_types",
     "../rtc_base",
     "../rtc_base:checks",
     "../rtc_base:rtc_base_tests_utils",
@@ -260,6 +270,7 @@
 
   deps = [
     ":rtc_p2p",
+    ":stun_types",
     "../rtc_base",
     "../rtc_base:checks",
     "../rtc_base/system:rtc_export",