fix: incorporate collaborative scaling overgeneration

[danielolsen]

Purpose

Calculate collaborative clean energy shortfall appropriately, where an overgeneration in one target area can be exported to offset shortfalls in another area.

What is the code doing

In powersimdata/scaling/clean_capacity_scaling/tests/test_strategies.py, we add a test case for which there is one zone with clean energy shortfall and one zone with clean energy overgeneration: test_collaborative_capacity_strategy_overgeneration(). This test is identical to that of test_collaborative_capacity_strategy(), except for the following lines:

• Line 585 sets the target for the Pacific target zone to 0.
• Line 597 confirms that the shortfall for the Pacific target zone is calculated as 0.
• Line 649 confirms the new collaborative shortfall value.
• Lines 654, 655, 659, 661, 663, and 665 confirm the new calculations based on this collaborative shortfall value.

In powersimdata/scaling/clean_capacity_scaling/auto_capacity_scaling.py , we correct the logic in CollaborativeStrategyManager.calculate_total_shortfall() to appropriately count the overgeneration in one zone against the shortfalls in the other area.

Time to review

Half an hour. There are only around 10 lines of real changes, the rest of the new code is a direct copy from the old test case.

[BainanXia]

The logic is clean. All tests passed. Just need to be aware that we are moving these files around in another ongoing PR #124 and this may cause conflicts when merging. @dmuldrew will be the best person to manage the order of merging these branches.