Temporarily move publishing to Helix build agents

[MattGal]

As seen in https://github.com/dotnet/core-eng/issues/13098 and the linked IcM ticket, we seem to have moved from WIN- to fv- machines and started hitting memory issues.

To double check:

• The right tests are in and and the right validation has happened. Guidance: https://github.com/dotnet/core-eng/tree/master/Documentation/Validation

[riarenas]

Do we have the capacity for this? 😮

[MattGal]

Do we have the capacity for this? 😮

Pretty sure in terms of cores and agent capacity we do, other than if you mean monetarily where I have no clue. This is way more expensive than using hosted since it's moving around ADO artifacts. I am simply preparing the PR to have it ready if we want to; it might be something we do via a custom non-main branch like before when the problem was disk space not memory.

[riarenas]

Yep makes sense. Was mostly worried about cores and wait times.

Maybe this is a good opportunity for another major overhaul for how we do the publishing. I'm sure @epananth would appreciate that. (not)