Replace bin/ build tooling

[olix0r]

When I wrote the bin/docker-* tooling, I was mostly doing so out of frustration and expediency. But, ultimately, there are better tools out there for this sort of thing that will be easier for folks to work with---especially new comers to the project.

My hunch is that we should use make (though, hopefully not one massive Makefile).

[siggy]

For reference: https://github.com/linkerd/linkerd2/blob/master/BUILD.md#build-architecture

[stale]

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