fix: Enable UDT schema tests to differentiate modules that uses the `…

…sys` namespace explicitely (Azure#760)

## Description

Some modules (like Compute Gallery) must use metadata annotations using
the `sys` namespace (e.g., @sys.description('...'). Up until now, when
testing the implementation against the schema, Pester would complain
about those cases. This was fixed by detecting if the `sys` namespace
was used and if so, updating the expected schema.

Before:

![image](https://github.com/Azure/bicep-registry-modules/assets/5365358/5db88faa-32bb-4cf5-b533-e5d39c8989ef)

After:

![image](https://github.com/Azure/bicep-registry-modules/assets/5365358/2d021b1e-aca7-44e5-9728-b7c6e5bf92a9)

---------

Co-authored-by: Erika Gressi <[email protected]>

avm/utilities/pipelines/staticValidation/compliance/module.tests.ps1

@@ -1101,6 +1101,11 @@ Describe 'Module tests' -Tag 'Module' {
           }
           $expectedSchema = $expectedSchemaFull[$expectedSchemaStartIndex..$expectedSchemaEndIndex]
 
+          if ($templateFileContentBicep -match '@sys\.([a-zA-Z]+)\(') {
+            # Handing cases where the template may use the @sys namespace explicitely
+            $expectedSchema = $expectedSchema | ForEach-Object { $_ -replace '@([a-zA-Z]+)\(', '@sys.$1(' }
+          }
+
           $formattedDiff = @()
           foreach ($finding in (Compare-Object $implementedSchema $expectedSchema)) {
             if ($finding.SideIndicator -eq '=>') {