Enhance UseDeclaredVarsMoreThanAssignments to detect also take into account the usage of Get-Variable with an array of variables and usage of named parameter -Name

[bergmeister]

PR Summary

Fixes #1301 by enhancing the parsing of the Get-Variable AST to also check if an array is passed or if the -Name parameter is used as a named parameter (including cases where it is shortened to -n).
Also refactored logic into it's own static method for better readability and performance.
Since reverse engineering a CommandAst into the used parameters is quite complex, I am not going to further enhance it.

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[rjmholt]

This makes me think we should really invest in some general purpose AST functionality (like parameter parsing/binding tools) (but probably don't have the time currently).

Otherwise, LGTM

[bergmeister]

Yes, I agree something like a parameter binder helper would be nice but I think it would require the runtime and be no purely static just based on the AST. Maybe some of the parameter binder functionality in PowerShell could be exposed?