Vendor binaries inside of the main executable

[moio]

Intent is to reduce the dependencies of dartboard to docker alone (and only in case the k3d backend is in use, otherwise no dependencies at all).

Summary of changes:

• teach make to download interesting binaries
• embed interesting binaries into golang executable
• upon run, extract embedded binaries into .bin
• when necessary, run embedded binaries from .bin

Last step is the biggest change, WIP.

[git-ival]

The changes seem solid so far, what mechanism did you have in mind for distributing dartboard itself (docker images)?

[moio]

Plain executable (like kubectl) and possibly docker image

[moio]

kubectl was fully adapted, helm too, k6 dropped.

Last one standing will be tofu. There question is: does it make sense to keep the tfexec baggage around or not?