Improve language server detection for workspace folders

[thecrypticace]

This PR should enable quicker booting of the language server in large multi-root workspaces

1. Potentially improved detection time in multi-root workspaces

Now we'll start the server as soon as any search has requested that it be started. Any remaining searches will be cancelled instead of waiting for them to complete. The language server itself will still do a more exhaustive search to find projects in all registered workspace folders.

2. Ignore pre-processor files that don't contain @config

Tailwind CSS v4 required us to analyze the workspace for more stylesheets that may contain @import (because @import "tailwindcss" and similar), @theme, etc… but these are only supported in .css files and not .styl, .sass, .scss, .less, etc…

We were already doing this because v3 looked for @config but that is valid in any stylesheet type. Now we restrict @import, @theme, etc matching to .css files and we'll be less likely to start the server if we don't need to.

[reslear]

maybe fix #1371

[solidprinciples]

@thecrypticace - facing this issue, was just delving into the codebase to understand further.

I found that hoisting the css file to monorepo root in my case (using nuxt/ui, installed from monorepo root) fixed it.

Seems like nuxt/ui was not resolving unless placed in the appropriate folder for project detection. Bootstraping a new nuxt app, non-mono repo, was able to resolve the additional nuxt-ui styles.