[pylint] Fixed false-positive on the rule PLW1641 (eq-without-hash) (#10566)

## Summary

Fixed false-positive on the rule `PLW1641`, where the explicit
assignment on the `__hash__` method is not counted as an definition of
`__hash__`. (Discussed in #10557).

Also, added one new testcase.

## Test Plan

Checked on `cargo test` in `eq_without_hash.py`.

Before the change, for the assignment into `__hash__`, only `__hash__ =
None` was counted as an explicit definition of `__hash__` method.
Probably any assignment into `__hash__` property could be counted as an
explicit definition of hash, so I removed `value.is_none_literal_expr()`
check.

Author: boolean-light

crates/ruff_linter/resources/test/fixtures/pylint/eq_without_hash.py

@@ -5,6 +5,7 @@ def __init__(self):
     def __eq__(self, other):
         return isinstance(other, Person) and other.name == self.name
 
+
 # OK
 class Language:
     def __init__(self):
@@ -16,8 +17,24 @@ def __eq__(self, other):
     def __hash__(self):
         return hash(self.name)
 
+
 class MyClass:
     def __eq__(self, other):
         return True
 
     __hash__ = None
+
+
+class SingleClass:
+    def __eq__(self, other):
+        return True
+
+    def __hash__(self):
+        return 7
+
+
+class ChildClass(SingleClass):
+    def __eq__(self, other):
+        return True
+
+    __hash__ = SingleClass.__hash__

crates/ruff_linter/src/rules/pylint/rules/eq_without_hash.rs

@@ -67,20 +67,21 @@ fn has_eq_without_hash(body: &[Stmt]) -> bool {
     let mut has_eq = false;
     for statement in body {
         match statement {
-            Stmt::Assign(ast::StmtAssign { targets, value, .. }) => {
+            Stmt::Assign(ast::StmtAssign { targets, .. }) => {
                 let [Expr::Name(ast::ExprName { id, .. })] = targets.as_slice() else {
                     continue;
                 };
 
-                // Check if `__hash__` was explicitly set to `None`, as in:
+                // Check if `__hash__` was explicitly set, as in:
                 // ```python
-                // class Class:
+                // class Class(SuperClass):
                 //     def __eq__(self, other):
                 //         return True
                 //
-                //     __hash__ = None
+                //     __hash__ = SuperClass.__hash__
                 // ```
-                if id == "__hash__" && value.is_none_literal_expr() {
+
+                if id == "__hash__" {
                     has_hash = true;
                 }
             }