Various refactorings to rustc_interface This should make it easier to move the driver interface away from queries in the future. Many custom drivers call queries like `queries.global_ctxt()` before they are supposed to be called, breaking some things like certain `--print` and `-Zunpretty` options, `-Zparse-only` and emitting the dep info at the wrong point in time. They are also not actually necessary at all. Passing around the query output manually would avoid recomputation too and would be just as easy. Removing driver queries would also reduce the amount of global mutable state of the compiler. I'm not removing driver queries in this PR to avoid breaking the aforementioned custom drivers.