[ty] infer name and value for enum members (#20311)

## summary
- this pr implements the following attributes for `Enum` members:
  - `name`
  - `_name_`
  - `value`
  - `_value_`
- adds a TODO test for `my_enum_class_instance.name`
- only implements if the instance is a subclass of `Enum` re: this
[comment](https://github.com/astral-sh/ruff/pull/19481#issuecomment-3103460307)
and existing
[test](c34449ed7c/crates/ty_python_semantic/resources/mdtest/enums.md (L625))

### pointers
- https://github.com/astral-sh/ty/issues/876
- https://typing.python.org/en/latest/spec/enums.html#enum-definition
- https://github.com/astral-sh/ruff/pull/19481#issuecomment-3103460307

## test plan
- mdtests
- triaged conformance diffs here:
https://diffswarm.dev/d-01k531ag4nee3xmdeq4f3j66pb
- triaged mypy primer diffs here for django-stubs:
https://diffswarm.dev/d-01k5331n13k9yx8tvnxnkeawp3
  - added a TODO test for overriding `.value`
- discord diff seems reasonable

---------

Co-authored-by: David Peter <mail@david-peter.de>

crates/ty_python_semantic/src/lib.rs

@@ -4,8 +4,6 @@
 )]
 use std::hash::BuildHasherDefault;
 
-use rustc_hash::FxHasher;
-
 use crate::lint::{LintRegistry, LintRegistryBuilder};
 use crate::suppression::{INVALID_IGNORE_COMMENT, UNKNOWN_RULE, UNUSED_IGNORE_COMMENT};
 pub use db::Db;
@@ -19,6 +17,7 @@ pub use program::{
     PythonVersionWithSource, SearchPathSettings,
 };
 pub use python_platform::PythonPlatform;
+use rustc_hash::FxHasher;
 pub use semantic_model::{
     Completion, CompletionKind, HasDefinition, HasType, NameKind, SemanticModel,
 };