Deprecate the after_crate_root_parsing callback

Several custom drivers are incorrectly calling queries.global_ctxt()
from inside of it, which causes some driver code to be skipped. As such
I would like to either remove it in the future or if custom drivers
still need it, change it to accept an &rustc_ast::Crate instead.

compiler/rustc_driver_impl/src/lib.rs

@@ -157,6 +157,8 @@ pub trait Callbacks {
     /// Called after parsing the crate root. Submodules are not yet parsed when
     /// this callback is called. Return value instructs the compiler whether to
     /// continue the compilation afterwards (defaults to `Compilation::Continue`)
+    #[deprecated = "This callback will likely be removed in the future. Use either \
+                    the after_expansion or the after_analysis callback instead."]
     fn after_crate_root_parsing<'tcx>(
         &mut self,
         _compiler: &interface::Compiler,