[bug] Split/merge operations on module-level comments (`//!`) don't work as expected

Rust-Analyzer doesn't seem to correctly operate on //! comments, which makes it hard to write module-level documentation and examples. I'm not sure if this is specifically an interaction between vscode.vim and RA, or general to the way RA works. But this did seem to work correctly when I still used RLS + vim.

Issues

The two main issues I encounter regularly are:

1. Splitting a long line into multiple lines using Vgq. This inserts a // comment instead of a //! comment.
2. Merging two shorter lines into a single line using Vjgq. This merges the lines, but leaves in a stray ! character.

Example

Both issues we've mentioned can be seen here. First we split a long line into multiple lines, which doesn't correctly insert a //! comment. And then we merge two shorter lines into a single line, which leaves a stray ! in the merged line.

Reproduce the two reported cases in a Rust module containing //! comments, using Vgq to split a long line and Vjgq to merge lines with the vscode.vim setup. Compare the results with the expected //! comments: splitting should preserve the prefix, and merging should not leave a stray !.