Formalize some more Drydock conditions and bookkeeping

Summary:
Ref T13677. Track which resources a given lease has begun allocating or reclaiming in a more formal way, and add logging for waiting actions.

The "allocating" mechanism is new. This will replace an existing similar "reclaiming" mechanism in a future change.

Test Plan: See followup changes.

Subscribers: yelirekim, PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13677

Differential Revision: https://secure.phabricator.com/D21806