This adds a `ql.name` codegen pragma to change the name of a property on
the QL side. This is useful to give more meaningful names than what we
get from the generated rust AST.
This generates test source files from code blocks in class docstrings.
By default the test code is generated as is, but it can optionally:
* be wrapped in a function providing an adequate context using
`@rust.doc_test_function(name, *, lifetimes=(), return_type="()", **kwargs)`,
with `kwargs` providing both generic and normal params depending on
capitalization
* be skipped altogether using `@rust.skip_doc_test`
So for example an annotation like
```python
@rust.doc_test_function("foo",
lifetimes=("a",),
T="Eq",
x="&'a T",
y="&'a T",
return_type="&'a T")
```
will result in the following wrapper:
```rust
fn foo<'a, T: Eq>(x: &'a T, y: &'a T) -> &'a T {
// example code here
}
```
This allows to group together related AST classes to reuse the same
test source and extraction. For example this is useful for
`EnumDecl/EnumCaseDecl/EnumElementDecl`, where this is applied to.
