Improve Rust highlight queries (#16747)

Release Notes:

- Add `@variable.parameter` highlight scope

![parameters are colored
pink](https://github.com/user-attachments/assets/68920017-b191-4779-9aa6-856831938480)

- Add `@attribute` highlight scope

![attributes are colored
yellow](https://github.com/user-attachments/assets/558d6ce0-5e4c-4ecb-893c-bc8f88d63829)

- Add markdown injection inside `doc_comment`s

![markdown
highlighting](https://github.com/user-attachments/assets/93ef4cf6-5ac1-46c6-80d0-82ca7bee0447)