Rebase: Uninstall existing non-editable versions when installing editable requirements bug (#682)

Separate branch for rebasing #677 onto main because i don't trust the
rebase enough to force push.

Closes #677.

---

If you install `black` from PyPI, then `-e ../black`, we need to
uninstall the existing `black`. This sounds simple, but that in turn
requires that we _know_ `-e ../black` maps to the package `black`, so
that we can mark it for uninstallation in the install plan. This, in
turn, means that we need to build editable dependencies prior to the
install plan.

This is just a bunch of reorganization to fix that specific bug
(installing multiple versions of `black` if you run through the above
workflow): we now run through the list of editables upfront, mark those
that are already installed, build those that aren't, and then ensure
that `InstallPlan` correctly removes those that need to be removed, etc.

Closes #676.

Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>

crates/distribution-types/src/resolution.rs

@@ -2,7 +2,6 @@ use rustc_hash::FxHashMap;
 
 use pep508_rs::Requirement;
 use puffin_normalize::PackageName;
-use requirements_txt::EditableRequirement;
 
 use crate::{BuiltDist, Dist, PathSourceDist, SourceDist};
 
@@ -60,31 +59,6 @@ impl Resolution {
         requirements.sort_unstable_by(|a, b| a.name.cmp(&b.name));
         requirements
     }
-
-    /// Return the set of [`EditableRequirement`]s that this resolution represents.
-    pub fn editable_requirements(&self) -> Vec<EditableRequirement> {
-        let mut requirements = self
-            .0
-            .values()
-            .filter_map(|dist| {
-                let Dist::Source(SourceDist::Path(PathSourceDist {
-                    url,
-                    path,
-                    editable: true,
-                    ..
-                })) = dist
-                else {
-                    return None;
-                };
-                Some(EditableRequirement::Path {
-                    path: path.clone(),
-                    url: url.clone(),
-                })
-            })
-            .collect::<Vec<_>>();
-        requirements.sort_unstable_by(|a, b| a.url().cmp(b.url()));
-        requirements
-    }
 }
 
 impl From<Dist> for Requirement {