Improve LSP tasks ergonomics

[SomeoneToIgnore]

• stopped fetching LSP tasks for too long (but still use the hardcoded value for the time being — the LSP tasks settings part is a simple bool key and it's not very simple to fit in another value there)

• introduced prefer_lsp language task settings value, to control whether in the gutter/modal/both/none LSP tasks are shown exclusively, if possible

Release Notes:

• Added a way to prefer LSP tasks over Zed tasks