feat: add ffmpeg.dll to delay load configuration (#46151)

feat: set ffmpeg.dll as a delay-loaded DLL

Updated the /DELAYLOAD linker config in BUILD.gn to set ffmpeg.dll
as a delay-loaded DLL. This reduces startup overhead and prevents unnecessary
loading when ffmpeg-related functionality is not used (e.g., the browser process
was unnecessarily loading it).

BUILD.gn

@@ -1246,7 +1246,7 @@ if (is_mac) {
         "//components/crash/core/app:run_as_crashpad_handler",
       ]
 
-      ldflags = []
+      ldflags = [ "/DELAYLOAD:ffmpeg.dll" ]
 
       libs = [
         "comctl32.lib",