This test fails on targets without unwinding because the proc macro was
compiled as the target, not the host. Some targets were explicitly
disabled to pass CI, but these directives are more general.
Fixes Fuchsia tests.
The lint-non-snake-case-crate test may emit a warning in stderr if the
target does not support unwinding
```
warning: building proc macro crate with `panic=abort` may crash the compiler should the proc-macro panic
```
Consequently, the test will fail on targets that don't support unwinding
as written.
This change prevents lint-non-snake-case-crate#proc_macro_ from running
on targets that don't support unwind by using the needs-unwind
directive.
Mainly so that it is easier to only run all `non-snake-case`-specific
tests but no other tests with:
./x test tests/ui/lint/non-snake-case
But also to reduce the size of the large `tests/ui/lint` directory. And
rename some tests to pass tidy, and remove them from
`src/tools/tidy/src/issues.txt`.
