chore: Remove "apiclient" package

[kruton]

apiclient package was created in 2014 as a stop-gap to help people transition from "apiclient" to googleapiclient. This transition should have been completed in the past 10 years.

However now this is creating package pollution that interferes with another PyPI package called api-client that also writes to …/site-packages/apiclient/ and conflicts with this package.

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Fixes #2485 🦕

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[kruton]

Rebased onto newest commit.

[kruton]

Rebased onto head

[daniel-sanche]

From #2485:

Thanks for putting the fix together, but unfortunately this repo contains legacy versions of our GCP libraries and is in maintenance mode, so we try not to make major changes here. Removing the apiclient alias would be a breaking change, which could have a large impact on existing user code, so it's not a change we'll be able to make at this time

If it's at all possible, I'd recommend trying to move to the more modern gapic libraries (This is the gapic equivalent of firebase admin). If that's not possible, you may be able to make a fork of this code to accomplish what you need