Remove DrydockPreallocatedHostBlueprintImplementation

Summary:
Ref T9253. This comes from a time before Almanac. Now that we have Almanac, it makes much more sense to put this logic there than to try to put it in Drydock itself.

Remove the preallocated host blueprint, a relic of a bygone time.

Test Plan: Grepped for callsites.

Reviewers: hach-que, chad

Reviewed By: hach-que, chad

Maniphest Tasks: T9253

Differential Revision: https://secure.phabricator.com/D14110