Description
Github refuses to list more than 1,000 files in a given directory listing.
As of this writing, its web interface reports that 1,260 entries are omitted from the printout for https://github.com/rust-lang/rust/tree/master/src/test/compile-fail
This has a simple fix: More subdirectories.
In particular, many of the tests even have a prefix that strongly implies a potential subdirectory to move that subset into; e.g. the associated-{const,item,type} tests could all go into associated-item/. LIkewise, the E0nnn test could all go into diagnostics/...
(This is a super easy change to make to the test suite, though I know that some people want to separately migrate more/all of the tests into the ui/ subdirectory. I no longer object to the latter migration, but we'll still need to resolve this problem even when we do that migration.)