[pylint] Also report when the object isn't a literal (PLE1310) (#15985)

## Summary

Follow-up to #15984.

Previously, `PLE1310` would only report when the object is a literal:

```python
'a'.strip('//')  # error

foo = ''
foo.strip('//')  # no error
```

After this change, objects whose type can be inferred to be either `str`
or `bytes` will also be reported in preview.

## Test Plan

`cargo nextest run` and `cargo insta test`.

crates/ruff_python_semantic/src/analyze/typing.rs

@@ -741,6 +741,22 @@ impl BuiltinTypeChecker for SetChecker {
     const EXPR_TYPE: PythonType = PythonType::Set;
 }
 
+struct StringChecker;
+
+impl BuiltinTypeChecker for StringChecker {
+    const BUILTIN_TYPE_NAME: &'static str = "str";
+    const TYPING_NAME: Option<&'static str> = None;
+    const EXPR_TYPE: PythonType = PythonType::String;
+}
+
+struct BytesChecker;
+
+impl BuiltinTypeChecker for BytesChecker {
+    const BUILTIN_TYPE_NAME: &'static str = "bytes";
+    const TYPING_NAME: Option<&'static str> = None;
+    const EXPR_TYPE: PythonType = PythonType::Bytes;
+}
+
 struct TupleChecker;
 
 impl BuiltinTypeChecker for TupleChecker {
@@ -984,6 +1000,16 @@ pub fn is_float(binding: &Binding, semantic: &SemanticModel) -> bool {
     check_type::<FloatChecker>(binding, semantic)
 }
 
+/// Test whether the given binding can be considered an instance of `str`.
+pub fn is_string(binding: &Binding, semantic: &SemanticModel) -> bool {
+    check_type::<StringChecker>(binding, semantic)
+}
+
+/// Test whether the given binding can be considered an instance of `bytes`.
+pub fn is_bytes(binding: &Binding, semantic: &SemanticModel) -> bool {
+    check_type::<BytesChecker>(binding, semantic)
+}
+
 /// Test whether the given binding can be considered a set.
 ///
 /// For this, we check what value might be associated with it through it's initialization and