Brakeman integration

[andyw8]

Rails 8 will add Brakeman: https://www.shakacode.com/blog/rails-8-adds-brakeman-by-default/

We could surface Brakeman's warnings within the editor.

Brakeman support should probably exist in a separate addon, but for initial investigation/prototyping it could be part of the ruby-lsp-rails addon.

The Guard plugin for Brakeman may be a useful reference understanding the APIs available: https://github.com/guard/guard-brakeman

[vinistock]

I think it's worth prototyping. However, I do have a performance concern with making this a default. We already pay a high price re-parsing documents a second time because RuboCop uses a different AST than the Prism one.

Brakeman would introduce a third parsing pass on every document, which has significant potential for slow downs.