Add tests for simple Cadl model with properties of various types

[annelo-msft]

@timotheeguerin shared instructions for adding Cadl tests here: https://github.com/Azure/autorest.testserver/wiki/Cadl-Scenario-Tests

This issue tracks the work to create a set of simple hello-world tests to support generating models with properties described in this issue:
Azure/autorest.csharp#2337 (comment), specifically:

• String
  Note: Should include sub-types for C# like url and Etag (exact list TBD). CADL express this with “format” modifier like Swagger does.
• bytes
• Int32
• Int64 (this format is highly discouraged by RestAPI board that prefers safeint/int53)
• Safeint (int53)
• Float32 (float in Swagger)
• Float64 (double in Swagger)
• zonedDateTime (a precise point in time with TZ)
  Note: RFC3339 if serialized in JSON or RFC2616 if serialized via a header.
• boolean
• array
• map

These tests should cover the cases where the model is an:

• Input model (only an input to a PUT operation)
• Output model (only an output from a GET operation)
• Input/output model (both an input to a PUT operation and an output from a GET operation)

So that languages that treat these differently can validate their scenarios for each, and their evolution story into input/output model.

[annelo-msft]

@lmazuel, @mikekistler FYI