[Feature Request] @alias hover description / search for description

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It would be really nice, to have a popup, when hovering over a `@alias`.

```
---@alias DeviceSide
---| '"left"' # The left side of the device
---| '"right"' # The right side of the device
---| '"top"' # The top side of the device
---| '"bottom"' # The bottom side of the device
---| '"front"' # The front side of the device
---| '"back"' # The back side of the device

---@param side DeviceSide
local function checkSide(side) end
```

**Hover description**
eg:
```
checkSide("left")
```
when hovering over "left", display a popup with the text: `The left side of the device`

**Search for description**
When beginning to type:
```
checkSide(left side
```

it would be great, if the IntelliSense would show the entry `"left" -- The left side of the device`

Start by tracing how the language server handles @alias declarations, hover information, and IntelliSense search suggestions. Reproduce the DeviceSide example and follow the existing paths for hovering over "left" and searching for "left side". Done means both the hover popup and description-based suggestion work for alias entries.

Written by the indexing model from the issue text.