unbranded emitter, write test cases

[weidongxu-microsoft]

Depends on #3000

Can refer to existing tests on azure-core https://github.com/microsoft/typespec/tree/main/packages/http-client-java/generator/http-client-generator-test/src/test

Temporary skip tests that cannot write or cannot pass.

[weidongxu-microsoft]

based on branch microsoft/typespec#5437

work folder packages/http-client-java/generator/http-client-generator-standard-test

setup script Setup.ps1

run test server npm run spector-serve

[weidongxu-microsoft]

Expect the test there be almost same of those in https://github.com/microsoft/typespec/tree/main/packages/http-client-java/generator/http-client-generator-test/src/test

There would be less tests, e.g. cases under azure or _specs_.azure or tsptest namespace will not be there. (I've also removed some tsp source that cannot compile)
Basically, if the ##Client is not there, that test can be deleted.

Also, don't copy tests under generated namespace.

Example