Introduce sysprof-cat

It's a simple CLI tool that dumps the contents of a Sysprof capture
file in a syntax inspired by GTK's render node syntax.

It prints metadata, the callgraph, marks, and counters. Other fields
may be added as needed, but for now this is sufficient for inspecting
WebKit captures.

There are CLI args for not printing particular groups, so that we can
filter out what we need.

src/meson.build

@@ -28,6 +28,7 @@ endif
 
 if get_option('tools')
   subdir('sysprof-agent')
+  subdir('sysprof-cat')
   subdir('sysprof-cli')
   subdir('sysprof-diff')
 endif