[PSE-245] Package mirror arguments for use in IPA build and execution

[dmorris-algo]

Five package mirror arguments are added to the builder image; CRAN_MIRROR is passed into langserver's environment during algorithm execution.

This supports both IPA algorithm builds and IPA algorithm executions:

• https://github.com/algorithmiaio/containers/pull/185
• https://github.com/algorithmiaio/docker-builder/pull/1
• https://github.com/algorithmiaio/node-autoscaler/pull/148

[pmcq]

don't worry about dockherder. but also in general - why do we need the mirror args at runtime? I would expect that users aren't installing more packages at runtime than they already did at compile. i think this might've been there because of some weirdness with R specifically, but the other languages can probably be removed (and hopefully we can remove R's too since it's sloooow)

[aslisabanci]

Tested the branch by running a previously successful "environment validator" script run to build a Pytorch package and it was successful.