Migrate to Arcade's blob publish infrastructure

[dagood]

The blob (installer and checksum) publish infra for Core-Setup official builds is custom, per dotnet/arcade#3630.

This should be moved over to take advantage of features built on top of it like dotnet/arcade#3963, and make the assets follow more well-understood flows so the build can be traced better through BAR.

(There is unfortunately not a significant maintenance cost reduction in doing this until all custom publish steps can be removed (integrated into Arcade). Specifically, when channels are added/removed, a corresponding change is necessary in Core-Setup or the build will either break or not publish when it should.)

/cc @mmitche

[dagood]

Completed Oct 2019 by dotnet/core-setup#8426.