A small optimization in the scheduler required users to specify specific
models of devices if the required count was higher than the individual
model/vendor on the node. This change removes that optimization to allow
for more intuitive device scheduling when different vendor/model device
types exist on a node.
This change isolates all the code that deals with node selection in the
scheduler into its own package called feasible.
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Co-authored-by: Tim Gross <tgross@hashicorp.com>
