Rename rustdoc lints to be a tool lint instead of built-in.

- Rename `broken_intra_doc_links` to `rustdoc::broken_intra_doc_links`
- Ensure that the old lint names still work and give deprecation errors
- Register lints even when running doctests

  Otherwise, all `rustdoc::` lints would be ignored.

- Register all existing lints as removed

  This unfortunately doesn't work with `register_renamed` because tool
  lints have not yet been registered when rustc is running. For similar
  reasons, `check_backwards_compat` doesn't work either. Call
  `register_removed` directly instead.

- Fix fallout

  + Rustdoc lints for compiler/
  + Rustdoc lints for library/

Note that this does *not* suggest `rustdoc::broken_intra_doc_links` for
`rustdoc::intra_doc_link_resolution_failure`, since there was no time
when the latter was valid.

src/test/rustdoc-ui/lint-missing-doc-code-example.rs

@@ -1,5 +1,5 @@
 #![deny(missing_docs)]
-#![deny(missing_doc_code_examples)]
+#![deny(rustdoc::missing_doc_code_examples)]
 
 //! crate level doc
 //! ```
@@ -19,7 +19,7 @@ fn test() {
 mod module1 { //~ ERROR
 }
 
-#[allow(missing_doc_code_examples)]
+#[allow(rustdoc::missing_doc_code_examples)]
 /// doc
 mod module2 {