chore(cleanup)!: Remove teeny-request in favor of gaxios / authclient

[ddelgrosso1]

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Fixes #<issue_number_goes_here> 🦕

[ddelgrosso1]

Attempt 2: this time with less breaking changes. Most of the changes here are removing the old teeny-request and authentication workflows and interfaces in favor of utilizing storage-transport and authclient / gaxios.

[ddelgrosso1]

Next milestone: get it compiling

[mindrunner]

This is the way!

[danielduhh]

Looks solid. returning GaxiosError instead of APIError seems like the only breaking change?

[ddelgrosso1]

@danielduhh there are a few but most of them are moving from teeny-request types to Gaxios types (like GaxiosError that you pointed out). I have not touched the publicly exposed API surfaces.