Further simplify the macros generated by `rustc_queries`
This doesn't actually move anything outside the macros, but it makes them simpler to read.
- Add a new `rustc_query_names` macro. This allows a much simpler syntax for the matchers in the macros passed to it as a callback.
- Convert `define_dep_nodes` and `alloc_once` to use `rustc_query_names`. This is possible because they only use the names
(despite the quite complicated matchers in `define_dep_nodes`, none of the other arguments are used).
- Get rid of `rustc_dep_node_append`.
r? `@cjgillot`
294f0eef73