Do not display PSScriptAnalyzer's whitespace analysis for the cursor's line

[rjmholt]

Moved over from PowerShell/PSScriptAnalyzer#1033.

We should filter out PSSA diagnostics complaining about whitespace on the cursor's current line.

[bergmeister]

Note that PR PowerShell/PSScriptAnalyzer#1048 would mean that this is not needed any more

[rjmholt]

Before I close this issue, we should decide if maybe we want to ignore diagnostics for the cursor's current line?

I suspect that the current script analysis experience probably isn't fast enough (as PSES implements it -- not a jab at PSSA) to keep up, so this would be a wild goose chase.