powershell.codeFormatting.whitespaceBetweenParameters inappropriately removes + operators in string concatenation

Issue Description

When formatting a document with powershell.codeFormatting.whitespaceBetweenParameters enabled, the formatter inappropriately removes + operators in string concatenation.

Steps to reproduce:

1. Enter this code example: Write-Output ($env:computername + ", " + $env:username) (GitHub is collapsing the whitespace, but there are four spaces on each side of each plus sign)
2. Enable powershell.codeFormatting.whitespaceBetweenParameters
3. Format document

Expected result:

Write-Output ($env:computername + ", " + $env:username)

Actual result:

Write-Output ($env:computername ", " + $env:username) (which is syntactically invalid!)

Additionally, if you start out with the expected result and format the document, you get the following result:

Write-Output ($env:computername ", " $env:username) …which is even worse, as the operators have been removed entirely.

Attached Logs

1593619176-7b7e0c1b-7340-41cb-a9a0-c526c1c513bd1593619173652.zip editor services.log

Environment Information

Visual Studio Code

Name	Version
Operating System	Windows_NT x64 10.0.19041
VSCode	1.46.1
PowerShell Extension Version	2020.6.0

PowerShell Information

Name	Value
PSVersion	5.1.19041.1
PSEdition	Desktop
PSCompatibleVersions	1.0 2.0 3.0 4.0 5.0 5.1.19041.1
BuildVersion	10.0.19041.1
CLRVersion	4.0.30319.42000
WSManStackVersion	3.0
PSRemotingProtocolVersion	2.3
SerializationVersion	1.1.0.1

Visual Studio Code Extensions

Visual Studio Code Extensions(Click to Expand)

Extension	Author	Version
powershell	ms-vscode	2020.6.0

[rjmholt]

I can reproduce with 1.19.0 but not with the latest version of master.

I trust you on this

[rjmholt]

> pwsh-preview.cmd
PowerShell 7.1.0-preview.5
Copyright (c) Microsoft Corporation.

https://aka.ms/powershell
Type 'help' to get help.

C:\Users\Robert Holt\Documents\Dev\Microsoft\PSScriptAnalyzer [master ≡ +3 ~0 -0 !]
> gmo PSSCriptAnalyzer
C:\Users\Robert Holt\Documents\Dev\Microsoft\PSScriptAnalyzer [master ≡ +3 ~0 -0 !]
> ipmo .\out\PSScriptAnalyzer\
C:\Users\Robert Holt\Documents\Dev\Microsoft\PSScriptAnalyzer [master ≡ +3 ~0 -0 !]
> Invoke-Formatter -ScriptDefinition 'Write-Output ($env:computername + ", " + $env:username)' -Settings @{
>>  Rules = @{
>>    PSUseConsistentWhitespace = @{
>>      Enable = $true
>>      CheckParameter = $true
>>    }
>>   }
>> }
Write-Output ($env:computername ", " + $env:username)

Looks like I can unfortunately