Sync eng/common directory with azure-sdk-tools for PR 9290 (#6158)

* identify and resolve missing function GenerateMatrixForConfig 
* identify and resolve miss-used null-coalesce operator

---------

Co-authored-by: Scott Beddall <scbedd@microsoft.com>

eng/common/scripts/job-matrix/Create-PrJobMatrix.ps1

@@ -64,7 +64,9 @@ $packageProperties = Get-ChildItem -Recurse "$PackagePropertiesFolder" *.json `
 
 # set default matrix config for each package if there isn't an override
 $packageProperties | ForEach-Object {
-  $_.CIMatrixConfigs = $_.CIMatrixConfigs ?? $configs
+  if (-not $_.CIMatrixConfigs) {
+    $_.CIMatrixConfigs = $configs
+  }
 }
 
 # The key here is that after we group the packages by the matrix config objects, we can use the first item's MatrixConfig

eng/common/scripts/job-matrix/job-matrix-functions.ps1

@@ -740,3 +740,28 @@ function Get4dMatrixIndex([int]$index, [Array]$dimensions) {
     return @($page3, $page2, $page1, $remainder)
 }
 
+function GenerateMatrixForConfig {
+    param (
+      [Parameter(Mandatory = $true)][string] $ConfigPath,
+      [Parameter(Mandatory = $True)][string] $Selection,
+      [Parameter(Mandatory = $false)][string] $DisplayNameFilter,
+      [Parameter(Mandatory = $false)][array] $Filters,
+      [Parameter(Mandatory = $false)][array] $Replace
+    )
+    $matrixFile = Join-Path $PSScriptRoot ".." ".." ".." ".." $ConfigPath
+
+    $resolvedMatrixFile = Resolve-Path $matrixFile
+
+    $config = GetMatrixConfigFromFile (Get-Content $resolvedMatrixFile -Raw)
+    # Strip empty string filters in order to be able to use azure pipelines yaml join()
+    $Filters = $Filters | Where-Object { $_ }
+
+    [array]$matrix = GenerateMatrix `
+      -config $config `
+      -selectFromMatrixType $Selection `
+      -displayNameFilter $DisplayNameFilter `
+      -filters $Filters `
+      -replace $Replace
+
+    return , $matrix
+}