This PR changes the default LSP for [someone13574/zed-verilog-extension](https://github.com/someone13574/zed-verilog-extension) to [slang-server](https://github.com/hudson-trading/slang-server), which was added a while ago but disabled due to being relatively new and having a few issues. Since those issues have been resolved, it is now becoming the default, replacing `verible` and `veridian`, which were previously used together. Additionally this is being done to disable `svls` by default, as it was added in https://github.com/zed-industries/extensions/pull/6820. Release Notes: - N/A --------- Co-authored-by: Kirill Bulatov <kirill@zed.dev>