[Typescript][Fetch] client refactoring

Created by: Place1

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
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Description of the PR

This PR applies a fork of typescript-fetch that I originally created here: https://github.com/place1/swagger-codegen-typescript-browser

The notable differences to the original typescript-fetch generator are outlines in the README.md

The changes in this fork also address the following open issues on this repo:

• #531
• #347 (closed)

TODO:

Confirm the this PR fixes the following known issues:

• swagger-api/swagger-codegen#8410 ensure that application/octet-stream responses come back as a blob
• swagger-api/swagger-codegen#2776 ensure that dates are deserialized
• swagger-api/swagger-codegen#7801 ensure that date params and date-array params are serialized

Add support for:

• swagger-api/swagger-codegen#7828 add method overload to allow caller to receive native Response
• break models and operations out into multiple files

General improvements:

• Find a better implementation for modelPropertyNaming. The current runtime conversion has known edge cases. Only a perfect implementation (i.e. based on the spec itself) should be acceptable for an option like modelPropertyNaming to exist.
• improve middleware api interface. use a single options object rather than many positional arguments