build(codegen): fix OpenAPI TypeError: error.response.data.on is not a function

[petermetz]

1. Stopped using the openapi-generator-cli package to download the .jar files
   and instead went with a direct download approach after having reverse
   engineered the HTTP URLs that can be used for fetching the jars from
   the maven repository.
2. The above appears to be a good fix because the third party service
   that was serving HTTP 504 errors was not the download link but the
   version validator link (e.g. a service that can tell us whether a
   specific version of the OpenAPI generator jar file exists or not). So,
   now that we just download exactly the versions of the .jars that we need
   there is no request sent to that other service and the problem therefore
   seems to have been solved.
3. We no longer need to delete the openapitools.json file in the root
   because it no longer gets created to begin with due to the change from 1
4. At this point it is really hard to tell if this is the last of this
   issue with the OpenAPI generator jar files, but one can hope.
5. Attempting to speed up the CI by optimizing the build-dev job:
   It is no longer doing bundle name validation nor the custom checks by
   default and it also skips linting and codegen entirely which are now done
   by separate jobs that can run in parallel. This should also reduce the
   load we place on the public utility service that is hosting the .jar files
   for the OpenAPI generator because this way the 40+ CI jobs that we have
   at the moment won't each download a pair of >20 MB .jar files every time.

Fixes #2525

Signed-off-by: Peter Somogyvari [email protected]