[REQ][typescript] Use more sophisticated yaml spec for typescript generators samples

[amakhrov]

Currently samples for all typescript generators are built based on petstore.yaml (2_0 and 3_0).
This spec doesn't include features like "date" format, allOf / oneOf, discriminators, enum aliases (for OAS3).

As a result, issues related to those features (e.g. #5171) are not obvious, and also it's not obvious how fixes addressing those issues impact the end result.

A number of other generators already use a more advanced test spec for that: petstore-with-fake-endpoints-models-for-testing

Suggestion is to change all existing typescript samples from petstore to petstore-with-fake-endpoints-models-for-testing

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