Migrate the CLI packaging system to the latest recommendation

[lmazuel]

I was randomly discussing packaging and CLI impact with @marstr, and I promised I will create an issue about the packaging update to do for CLI. So here it is :)

This means getting rid of azure_bdist_wheel file, using PEP420 for Python 3, etc. A more complete rational can be found here:
https://github.com/Azure/azure-sdk-for-python/wiki/Azure-packaging

I wouldn't say it's urgent, being that it doesn't impact at all the installers (Windows MSI, homebrew, etc.). Main benefits are :

• For service team development, since it will simplify the dev_setup.py (remove this kind of black magic). pip install --force-reinstall azure-nspkg==1.0.0 should never be needed anymore.
• Could simplify the "pip install" scenario in some corner case (shouldn't be considered a big concern)

Note that azure_bdist_wheel file logic is broken since an update of setuptools in November 2017, so we could consider as a benefit too removing a file that adds no value and just noise.

[yonzhan]

@fengzhou-msft add to S162.

[fengzhou-msft]

will work on this when support for Python 2 is removed.

[jeffb4]

Just to note, this does impact an internal Python project we wrote because we call out to the azure-cli and thus have this project as a listed dependency (which forces back our setuptools).

So while it surely isn't critical, I'd love to see it.

[fengzhou-msft]

resolved in version 2.11.0.