support rust-analyzers runnables extension #2577
Description
documented here https://rust-analyzer.github.io/book/contributing/lsp-extensions.html#runnables
this is supported by zed, though it currently has some problems that im working on fixing. we could have a runnable for each build step in the project, maybe with some extra integration like surfacing test failures as diagnostics actually that doesn't make sense the client is the one that runs the command