Disallowing per_alloc for host volumes in some cases makes life of a nomad user much harder.
When we rely on the NOMAD_ALLOC_INDEX for any configuration that needs to be re-used across
restarts we need to make sure allocation placement is consistent. With CSI volumes we can
use the `per_alloc` feature but for some reason this is explicitly disabled for host volumes.
Ensure host volumes understand the concept of per_alloc
Add a `PerAlloc` field to volume requests that directs the scheduler to test
feasibility for volumes with a source ID that includes the allocation index
suffix (ex. `[0]`), rather than the exact source ID.
Read the `PerAlloc` field when making the volume claim at the client to
determine if the allocation index suffix (ex. `[0]`) should be added to the
volume source ID.
In a deployment with two groups (ex. A and B), if group A's canary becomes
healthy before group B's, the deadline for the overall deployment will be set
to that of group A. When the deployment is promoted, if group A is done it
will not contribute to the next deadline cutoff. Group B's old deadline will
be used instead, which will be in the past and immediately trigger a
deployment progress failure. Reset the progress deadline when the job is
promotion to avoid this bug, and to better conform with implicit user
expectations around how the progress deadline should interact with promotions.
