YAGNI active_resolve_capabilities

This leaks a lot of LSP details into ide layer, which we want to avoid:

c9cec381bc/docs/dev (lsp-independence)

Additionally, all what this infra does is providing a toggle for
auto-import completion, but we already have one!

crates/ide/src/lib.rs

@@ -82,8 +82,8 @@ pub use crate::{
 };
 pub use assists::{Assist, AssistConfig, AssistId, AssistKind};
 pub use completion::{
-    CompletionConfig, CompletionItem, CompletionItemKind, CompletionResolveCapability,
-    CompletionScore, ImportEdit, InsertTextFormat,
+    CompletionConfig, CompletionItem, CompletionItemKind, CompletionScore, ImportEdit,
+    InsertTextFormat,
 };
 pub use hir::{Documentation, Semantics};
 pub use ide_db::base_db::{