Inconsistent version files

[ocelotl]

Some packages have their versions in a __init__.py file like this:

https://github.com/open-telemetry/opentelemetry-python/blob/main/opentelemetry-api/src/opentelemetry/version/__init__.py

Others have it in a version.py file like this:

https://github.com/open-telemetry/opentelemetry-python/blob/main/exporter/opentelemetry-exporter-opencensus/src/opentelemetry/exporter/opencensus/version.py

Make them consistent. Update the release scripts to take into consideration this change.

[ocelotl]

duplicate of #4097