Update Rust toolchain to 1.89 (#15157)

## Summary

Bumps Rust toolchain to 1.89, but not the MSRV.

Lifetime changes is related to a new lint rule explained in
https://blog.rust-lang.org/2025/08/07/Rust-1.89.0/#mismatched-lifetime-syntaxes-lint

## Test Plan

Existing Tests

crates/uv-resolver/src/lock/mod.rs

@@ -3934,7 +3934,7 @@ enum SourceDist {
 }
 
 impl SourceDist {
-    fn filename(&self) -> Option<Cow<str>> {
+    fn filename(&self) -> Option<Cow<'_, str>> {
         match self {
             Self::Metadata { .. } => None,
             Self::Url { url, .. } => url.filename().ok(),