Add linter rule for anonymous models

[catalinaperalta]

It would be great to have a linter rule call out anonymous models to help service teams avoid them as they define their spec, since this causes issues with the emitters later on. Based on this previous issue https://github.com/Azure/typespec-azure-pr/issues/2367 seems it is hard to catch all cases of anonymous models and this linter rule cannot warn for every case, but it would be useful to try to catch common scenarios where anonymous models cause issues for emitters, such as inline anonymous models passed into the standard templates.

[catalinaperalta]

After talking to @timotheeguerin, seems like these might be best added as part of TCGC linter rules. If so, we'd need to have azure specs extend those linter rules as well. This issue could help with how we extend these additional rules: microsoft/typespec#3011

[iscai-msft]

Removing the tcgc label from this, because "spread is spread" largely gets away from this issue for tcgc generation.