Remove special-casing for editable requirements (#3869)

## Summary

There are a few behavior changes in here:

- We now enforce `--require-hashes` for editables, like pip. So if you
use `--require-hashes` with an editable requirement, we'll reject it. I
could change this if it seems off.
- We now treat source tree requirements, editable or not (e.g., both `-e
./black` and `./black`) as if `--refresh` is always enabled. This
doesn't mean that we _always_ rebuild them; but if you pass
`--reinstall`, then yes, we always rebuild them. I think this is an
improvement and is close to how editables work today.

Closes #3844.

Closes #2695.

crates/uv-resolver/src/lib.rs

@@ -1,5 +1,4 @@
 pub use dependency_mode::DependencyMode;
-pub use editables::BuiltEditableMetadata;
 pub use error::ResolveError;
 pub use exclude_newer::ExcludeNewer;
 pub use exclusions::Exclusions;
@@ -25,7 +24,6 @@ mod candidate_selector;
 
 mod dependency_mode;
 mod dependency_provider;
-mod editables;
 mod error;
 mod exclude_newer;
 mod exclusions;