This is a small devex improvement to the rust code generator.
Usage of `sorted` in `rustgen.py` was causing the generated code to be
completely reshuffled on renames, which made diffs hard to follow. As an
example see [this generated file diff](https://github.com/github/codeql/pull/19059/files#diff-c938ba77a3398dd4c633ada5702a03477705c24740a2f7d1e40d4b270d8c3f86).
This will make the order deterministically based on the order of
definitions in the schema file. This means that renames will find the
same place in the generated file, and the place in the generated file
will generally be more predictable with respect to the schema.
However, that does mean this change is heavily reshuffling the generated
code.
By using the `rust.detach` pragma on a property, we make that property
not appear in the generated struct as a field, and provide instead
a `generated::Class::emit_property` function that can be used to emit
the corresponding TRAP entry independently.
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
}
```
