Make < exclusive for non-prerelease markers (#1878)

## Summary

Even when pre-releases are "allowed", per PEP 440, `pydantic<2.0.0`
should _not_ include pre-releases. This PR modifies the specifier
translation to treat `pydantic<2.0.0` as `pydantic<2.0.0.min0`, where
`min` is an internal-only version segment that's invisible to users.

Closes https://github.com/astral-sh/uv/issues/1641.

crates/uv-resolver/src/prerelease_mode.rs

@@ -95,4 +95,15 @@ impl PreReleaseStrategy {
             ),
         }
     }
+
+    /// Returns `true` if a [`PackageName`] is allowed to have pre-release versions.
+    pub(crate) fn allows(&self, package: &PackageName) -> bool {
+        match self {
+            Self::Disallow => false,
+            Self::Allow => true,
+            Self::IfNecessary => false,
+            Self::Explicit(packages) => packages.contains(package),
+            Self::IfNecessaryOrExplicit(packages) => packages.contains(package),
+        }
+    }
 }