Add a list of suppressions for each dianostic

[t-lipingma]

Steps to reproduce

Now I suppressed one rule twice in “function start-bar”.

1. PowerShell script: build.ps1

[System.Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSAvoidUsingWriteHost', '', Scope='Function', Target='start-ba[rz]',Justification="aa")]
[System.Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSAvoidUsingWriteHost', '', Scope='Function', Target='start-bar',Justification="bb")]
param()
function start-foo {
    write-host "start-foo"
}

function start-bar {
    write-host "start-bar"
}

function start-bam {
    write-host "start-bam"
}

2. if you already import the module, may skip this step.

Import-Module .\out\PSScriptAnalyzer\1.20.0\PSScriptAnalyzer.psd1

3. run PSScriptAnalyzer to analyze build.ps1. If not add -SuppressedOnly parameter, it only outputs non-suppressed results. So I add -SuppressedOnly parameter to see suppressed results.

Invoke-ScriptAnalyzer D:\build.ps1 -Recurse -SuppressedOnly

Expected behavior

RuleName                            Severity     ScriptName Line  Justification              
--------                            --------     ---------- ----  -------------                                      
PSAvoidUsingWriteHost               Warning      build.ps1  9     aa;bb   

If one rule suppressed twice in the same line, it needs to have a list of suppressions for the diagnostic.

Actual behavior

RuleName                            Severity     ScriptName Line  Justification              
--------                            --------     ---------- ----  -------------                                      
PSAvoidUsingWriteHost               Warning      build.ps1  9     aa                                         
PSAvoidUsingWriteHost               Warning      build.ps1  9     bb                             

The results seem like the existing implementation generates an output for each suppression, rather than each diagnostic.
So it's maybe better to have a list of suppressions for each diagnostic.

Environment data

> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      5.1.19041.1023
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.19041.1023
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

[rjmholt]

Although this would be a breaking change, I think the proposed change is relatively minor and makes sense.