Add option for generated enum types

[gslaszlo]

Add support for generated enum types, as in orval docs.

[CLAassistant]

All committers have signed the CLA.

[DefCon-007]

@gslaszlo Thanks a lot for the changes. The changes look good. I will try to test it locally once, meanwhile, can you add some unit tests for this? We can add some functional tests like this, https://github.com/grafana/openapi-to-k6/blob/main/tests/functional-tests/test-generator/generator.test.ts, we could take a single schema and test it out for all the supported enum types.

[gslaszlo]

@DefCon-007 Thanks for pointing it out, I've added tests for all 3 cases. I didn't want to do a lot of edits in the generator.test.ts so I added 3 fixtures with different expected_sdk params, but if you prefer to add more code instead of fixtures, I can do that as well.

[DefCon-007]

@gslaszlo Could you fix the conflicts? We are good to merge once they are fixed.

[gslaszlo]

@DefCon-007 Sorry for the delay, fixed the conflicts.