Temporarily disable UPF feature and tests on firecracker-v1.4.1-vhive-integration branch

[CuriousGeorgiy]

Summary

UPF feature for vanilla firecracker requires a separate integration effort (#807), so temporarily disable this feature and all tests for it.

Implementation Notes ⚒️

• vHive and the vHive and orchestrator tests now exit with an error when UPF is enabled.
• Tests using UPF are simply commented out.

External Dependencies 🍀

• N/A.

Breaking API Changes ⚠️

• N/A.

[ustiugov]

approved. @char-1ee please take a note. You'd need to re-enable it for firecracker v1.4 hypervisor as one of the goals of your project. We need to do that ASAP.
@BenjaminChun you also need to keep this in mind.

For the vHive community:
Note that we don't drop support for user page faults. However, we expect them to be less stable before @char-1ee completes his task.

[CuriousGeorgiy]

Please note this is not part currently part of the main branch, this is part of the firecracker-v1.4.1-vhive-integration branch, where vanilla firecracker snapshots will be introduced.

When UPF support is added, the firecracker-v1.4.1-vhive-integration branch will be merged to the main branch.

[ustiugov]

@CuriousGeorgiy I would prefer this to appear in main (when you are done with your changes) while having a branch vhive-userpagefaults-legacy for the legacy functionality users. also, the two branches need to be documented in the main README. and also document the remote snaps support limitations, i.e., what's to be done there.

We should pay attention to the new version so that it doesn't become stale. the legacy one works and no need to upgrade it. think of k8s/knative upgrade, for example