Switch v1 branches to use go modules

The v1 branches were migrated to use dep while that was the prospective new dependency tool. Now that go modules has reached a point of stabilization and is the defacto currently used tool, we should switch the v1 branches to it as it is becoming more difficult to use dep to maintain v1 because dep is not actively maintained.

Start by inspecting the v1 branches and their current dep configuration, then review how Go modules are introduced and maintained for those branches. The work is done when the v1 branches use Go modules instead of dep and their existing builds and tests continue to pass.

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