Generic method type parameter support

[andyleejordan]

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PR https://github.com/PowerShell/PowerShell/pull/12412#issuecomment-1023470022 introduced support for supplying type parameters to generic methods, e.g.:

[Array]::Empty[int]()

While it kind of looks like it's already working ([int] is being highlighted the same way as [Array]) we should check for any edge cases and probably add some tests.