Merge 'Fix some Rust compilation warnings' from Samuel Marks

Nothing fancy yet, assuming you merge this I'll do this one next:
```
warning: function pointer comparisons do not produce meaningful results since their addresses are not guaranteed to be unique
   --> core/types.rs:403:5
    |
398 | #[derive(Debug, Clone, PartialEq)]
    |                        --------- in this derive macro expansion
...
402 |     pub step_fn: StepFunction,
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
403 |     pub finalize_fn: FinalizeFunction,
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the address of the same function can vary between different codegen units
    = note: furthermore, different functions could have the same address after being merged together
    = note: for more information visit <https://doc.rust-lang.org/nightly/core/ptr/fn.fn_addr_eq.html>
```
And fix a test failure that I resolved in Python (specific to macOS
hosts). Basically this PR is putting my toe in the water to see how open
you are to contribs!

Closes #3211

core/incremental/operator.rs

@@ -2050,13 +2050,13 @@ impl AggregateOperator {
             .join(",")
     }
 
-    fn seek_key_from_str(&self, group_key_str: &str) -> SeekKey {
+    fn seek_key_from_str(&self, group_key_str: &str) -> SeekKey<'_> {
         // Calculate the composite key for seeking
         let key_i64 = self.generate_storage_key(group_key_str);
         SeekKey::TableRowId(key_i64)
     }
 
-    fn seek_key(&self, row: HashableRow) -> SeekKey {
+    fn seek_key(&self, row: HashableRow) -> SeekKey<'_> {
         // Extract group key for first row
         let group_key = self.extract_group_key(&row.values);
         let group_key_str = Self::group_key_to_string(&group_key);