Tracking issue for "minimize the rust-std component"

[Centril]

This tracks the issue for doing the stuff mentioned in #64823.

Also relevant:

• Rust platform size #61978
• The total Rust archive size has intensified recently #62486
• 3rd party objects missing from nightly-2019-10-12 #65335
• Package non-rust objects #65337
• https://discordapp.com/channels/442252698964721669/443148290352218115/632573542218858527

[Mark-Simulacrum]

This has essentially be done and should be in stable this or next cycle (I forget, to be honest).