`module()` function isn't respected by the language server

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### How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

### Which OS are you using?

Linux

### What is the issue affecting?

Diagnostics/Syntax Checking

### Expected Behaviour

When `module()` is used in a script, functions defined "globally", like so:
```lua
module("MyExampleModule")

function HelloWorld() end
```
Are understood by the language server to belong to the table at `_G.MyExampleModule`

### Actual Behaviour

Using the above example, the language server incorrectly believes `HelloWorld()` is at `_G.HelloWorld()` as opposed to `_G.MyExampleModule.HelloWorld()`

### Reproduction steps

1. Copy the above example into a file
2. Create another file in the same workspace
3. Type "Hello"
4. Observe that the autocomplete suggests the function `_G.HelloWorld()`, which does not exist

### Additional Notes

This cannot be worked around with `setfenv()`

### Log File

N/A

Reproduce the issue in the Visual Studio Code extension using the two-file example and the autocomplete step described. Trace how module("MyExampleModule") is handled during diagnostics and completion, then verify that HelloWorld is suggested under _G.MyExampleModule rather than _G.HelloWorld.

Written by the indexing model from the issue text.