add option Lua.hint.awaitPropagate to propagate ---@async

[findstr]

This option is disabled by default.
When disabled, it has no impact on performance.
When enabled, due to its upward propagation characteristics,
it may render some await-in-sync diagnostics ineffective,
but not all of them.
See Discussion #2981 .

[findstr]

I will further test additional edge cases.