build: move libcc patches to electron repo (#14104)

In the GN build, libchromiumcontent is no longer a distinct library, but
merely a container for a set of scripts and patches. Maintaining those
patches in a separate repository is tedious and error-prone, so merge
them into the main repo.

Once this is merged and GN is the default way to build Electron, the
libchromiumcontent repository can be archived.

patches/common/skia/dcheck.patch

@@ -0,0 +1,13 @@
+diff --git a/include/core/SkPostConfig.h b/include/core/SkPostConfig.h
+index c34397cde6..5a55535eeb 100644
+--- a/include/core/SkPostConfig.h
++++ b/include/core/SkPostConfig.h
+@@ -18,7 +18,7 @@
+     #ifdef NDEBUG
+         #define SK_RELEASE
+     #else
+-        #define SK_DEBUG
++        #define SK_RELEASE
+     #endif
+ #endif
+