AEM: Fix regex to be case insensitive

[MSSedusch]

Description

The regular expressions to extract the resource group and the resource name from a resource id were case sensitive. In some cases, the cmdlet was not able to install the extension because the resource id of e.g. disks had a lowercase resourcegroups in the resource id.

Fix for issue #8926

Checklist

• I have read the Submitting Changes section of CONTRIBUTING.md
• The title of the PR is clear and informative
• The appropriate change log has been updated
• The PR does not introduce breaking changes
• If applicable, the changes made in the PR have proper test coverage
• For public API changes to cmdlets:
  • the changes have gone through a cmdlet design review (Microsoft internal partners only)
  • the cmdlet markdown files were generated using the platyPS module