Auto merge of #62179 - alexcrichton:less-travis-appveyor, r=pietroalbini

Auto merge of #62179 - alexcrichton:less-travis-appveyor, r=pietroalbini

ci: Move most builders to Azure Pipelines

This commit disables all builders on Travis and almost all builders on
AppVeyor now that they're all running on Azure Pipelines. There is one
remaining builder on AppVeyor which hasn't been migrated yet due to a
test failure on Azure, which we'll be debugging soon. One remaining
builder is left on Travis which is the tools builder whenever a
submodule is changed, but we'll probably turn that off soon since it's
just for PRs.

The other major change in this PR is that the auto builders on Azure are
now configured with "real" prod credentials which should cause them to
publish all artifacts into the official CI buckets.