Enhance PSUseConsistentWhiteSpace to exclude more special cases when using unary operators

Found when discussing PR #949 , which already tweaked PSUseConsistentWhiteSpace when using unary operators inside parenthesis.
This adds another special case where the rule should be excluded. The community is welcome to provide more cases that need to be treated specially.

Steps to reproduce

Invoke-Formatter -ScriptDefinition '$r = $a -lt -$var'                                                                                                       

Expected behavior

$r = $a -lt -$var

Actual behavior

$r = $a -lt - $var

Environment data

This applies also to the latest version of the development branch.

> $PSVersionTable
Name                           Value
----                           -----
PSVersion                      5.1.16299.251
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.16299.251
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

> (Get-Module -ListAvailable PSScriptAnalyzer).Version | ForEach-Object { $_.ToString() }
1.16.1

使用所示的脚本定义，通过 Invoke-Formatter 和 PSUseConsistentWhiteSpace 规则重现该问题。跟踪 formatter 对一元运算符表达式的行为，并验证完成的更改能够保留 $r = $a -lt -$var，而不会在一元减号与 $var 之间插入空格。