Global variables are erroneously reported as "never used"

System Details Output

### VSCode version: 1.36.1 2213894ea0415ee8c85c5eea0d0ff81ecc191529 x64

### VSCode extensions:
bierner.lit-html@1.11.0
mikeburgh.xml-format@1.0.2
MS-CEINTL.vscode-language-pack-de@1.36.2
ms-vscode.powershell@2019.5.0
msjsdiag.debugger-for-chrome@4.11.6
slevesque.vscode-hexdump@1.7.2


### PSES version:

### PowerShell version:

Name                           Value
----                           -----
PSVersion                      5.1.16299.1146
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.16299.1146
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

Issue Description

PowerShell extension reports global variables as assigned but not used when they are not used from within a .psm1 module file. However, global variables may be used by scripts outside that module importing it.

Expected Behaviour

Global variables should never be reported as being unused.

Actual Behaviour

PowerShell extension reports global variables as assigned but not used when they are not used from within a .psm1 module file.

No source files, tests, or entry points are named. Start by locating the analyzer logic that reports assigned-but-unused variables and the tests covering module or global-variable scope. Confirm the current behavior, then update the relevant test expectations so global variables are not reported as unused and run the affected analyzer tests.