tsp - add support for anonymous object/dicts

[dolauli]

This pull request introduces improvements to the handling of dictionary and record model schemas in the TypeSpec Powershell converter. The changes focus on correctly managing anonymous dictionary schemas, enhancing property naming conventions, and ensuring proper schema creation for record models.

Schema handling improvements:

• Skipped processing of anonymous dictionary schemas by adding a check for the absence of the language property in dictionary schemas within convertor.ts.
• For record model types named Record, ensured a distinct schema is created and cached, improving the handling of anonymous records in modelUtils.ts.
• In getSchemaForRecordModel, added logic to only set the default property for named record types, ensuring anonymous dictionaries are treated correctly.

Property naming and description enhancements:

• Updated property schema naming to concatenate the model name and property name, resulting in more descriptive property names.
• Improved property description assignment by falling back to the schema's default description when documentation is missing.