feat: asyncify pickers - except for live_grep (#709)

* something kind of works already

* yayayayayayayayayayayayayayayayayayayayayayayayayayayayayayayayaya

* use async for everything besides live jobs

* fix: fixup autocmds previewer

* fix: lints for prime

* temp: Add example of how we can think about async sorters

* feat: Allow picker to decide when to cancel

* fix: simplify scoring logic and tests

* fixup: name

* fix: Move back towards more backwards compat methods

* fixup: Remove results from opts

* fixup: remove trailing quote

* fixup: Attempt to clean up some more async items. Next is status

* wip: Add todo for when bfredl implements extmarks over the EOL

* wip

* fixup: got em

* fixup: cleaning

* fixup: docs

lua/tests/automated/telescope_spec.lua

@@ -100,7 +100,12 @@ describe('telescope', function()
     describe('fzy', function()
       local sorter = require'telescope.sorters'.get_fzy_sorter()
       local function score(prompt, line)
-        return sorter:score(prompt, {ordinal = line})
+        return sorter:score(
+          prompt,
+          {ordinal = line},
+          function(val) return val end,
+          function() return -1 end
+        )
       end
 
       describe("matches", function()