Add protoSrcsDir config option

[codersasha]

Add a new config option, protoSrcsDir, which optionally limits the scope of proto file searches from {workspaceRoot}/** down to {workspaceRoot}/path/to/protos/**. This fixes an issue where autocompletion and go-to-definition calls are unuseably slow (upwards of 30 seconds) in repos with large numbers of ignored files (e.g. node_modules, bazel-out). With this fix, they are instant.

The "proper" way to fix this would be to respect VSCode's existing ignore lists in settings.json, but I'm not sure how to do that with fastglob in a way that actually improves performance. So, this solves the issue for now :)

[Qtax]

Something like this is badly needed for our monorepo. Without it "go to definition" is extremely slow, taking 10-30 seconds. Even when the definition is in the same file. 😅