Too strict regular expression used when searching for command groups

[FumingZhang]

The tool uses predefined regular expressions to search for command groups. However, it strictly limits the expression that declares the command group should not have newlines.

Code https://github.com/Azure/azure-cli-dev-tools/blob/dev/azdev/operations/regex.py#L147-L148

Example https://dev.azure.com/azclitools/public/_build/results?buildId=135332&view=logs&j=168ccbe3-da49-5c0b-6478-08f7016e4bf5&t=10a595be-4223-5cc7-9a73-012871b6eaee&l=154