[MPG][Diff] default value in Typespec, Swagger and SDK

[msyyc]

TypeSpec could use = to define default value for optional properties of a model or parameter, it equals to default of swagger like:

default value of both Typespec and swagger means server will use it instead of client side:

• Python SDK from typespec:
  

• Python SDK from swagger:
  

We can see there is difference between SDK generated from swagger and Typespec. I think the root cause is that m4 provides defaultValue while TCGC not: