[Bug]: Incorrect usage of additionalProperties and suppression of `no-empty-model` linting rule

### Describe the bug

https://github.com/search?q=repo%3AAzure%2Fazure-rest-api-specs%20typespec-azure-resource-manager%2Fno-empty-model&type=code

Most of the bad usages should be using `Record` or `Record`. We need to work with service team to correct them.

### Reproduction

https://github.com/search?q=repo%3AAzure%2Fazure-rest-api-specs%20typespec-azure-resource-manager%2Fno-empty-model&type=code

### Tasks

- [ ] Add linter warn of using `Record` instead of `Record`
- [ ] For `{}` handling, to avoid breaking changes, suggest CodeGen/TCGC has an optional flag to treat `{}` as void.

### 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 bug in the typespec language or core libraries file it in the [TypeSpec repo](https://github.com/Microsoft/TypeSpec/issues/new/choose)
- [x] Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
- [x] The provided reproduction is a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) of the bug.

Start with the linked repository code search for `typespec-azure-resource-manager/no-empty-model` and review the existing lint handling for `additionalProperties`, `Record`, and `Record`. Confirm the expected warning and investigate the mentioned CodeGen/TCGC optional flag for `{}` handling; done means the requested lint guidance and compatibility behavior are defined and covered by the relevant checks.

Written by the indexing model from the issue text.