Remove older Tanka libraries

[rfratto]

The "v0" and v1 libs have been deprecated for a while, and I think the v2 configs landed on a good design.

Note that the smoke folder currently sits alongside the v0 libs, but is not deprecated and should not be removed.

We should remove all the deprecated stuff and replace it with:

production/tanka/grafana-agent/ 
  testbed/       # previously smoke/
  internal/      # previously v2/internal/
  main.libsonnet # previously v2/main.libsonnet 
  README.md      # previously v2/README.md 

cc @rlankfo for your opinion on me renaming smoke to testbed, since I'm not sure "smoke test" is really an accurate name for what that environment is.

Alternatively, production/tanka/grafana-agent/smoke can be moved to a higher folder, such as production/tanka/grafana-agent-testbed or production/tanka/grafana-agent-smoke.

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[rlankfo]

cc @rlankfo for your opinion on me renaming smoke to testbed, since I'm not sure "smoke test" is really an accurate name for what that environment is.

+1 for renaming smoke to something like testbed, testkit, or testenv.

[rfratto]

This was done a few months ago. Closing as complete.