Lint for non-standard array encoding in greenfield tsp

### Clear and concise description of the problem

As defined in https://github.com/Azure/typespec-azure/issues/3535.

e.g. `ArrayEncoding.commaDelimited` and others are being added for compat with brownfield services. We should not allow these encodings by default for greedfield.

### Checklist

- [x] Follow our [Code of Conduct](https://github.com/azure/typespec-azure/blob/main/CODE_OF_CONDUCT.md)
- [x] Check that this issue is about the Azure libraries for typespec. For feature request in the typespec language or core libraries file it in the [TypeSpec repo](https://github.com/Microsoft/TypeSpec/issues/new/choose)
- [x] Read the [docs](https://azure.github.io/typespec-azure/).
- [x] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

Start by reading the requirements in Azure/typespec-azure#3535 and the TypeSpec Azure lint configuration or rules referenced by this issue. Identify where greenfield array encoding validation is defined, then verify that non-standard encodings such as ArrayEncoding.commaDelimited are rejected by default while brownfield compatibility remains possible.

Written by the indexing model from the issue text.