WIP: Plumb HTTP proxy configuration from host into VM environment

[tstromberg]

Detect system proxy configuration from environment, and plumb them into the docker env and /etc/environment within the VM by default.

Proxies are tricky, so this will no doubt will require future improvements for various edge cases.

This addresses countless bugs that I'm sick of commenting on, but most of all it closes #3242

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[afbjorklund]

195 files changed, 52464 insertions(+), 13462 deletions(-)

I'm thinking something went wrong here, with that vendor dep ?

[tstromberg]

Things to address:

• minikube should respect the discovered proxy
• minikube should not plumb 127.0.0.1 as a proxy value
• fix sys deps
• more testing

[tstromberg]

Closing until I have bandwidth to look into this again.