Add tolerance for high humidity OA control

[mjwitte]

Pull request overview

• Fixes OA controller high humidity control needs a tolerance #7644
• The high humidity control option in Controller:OutdoorAir would somewhat randomly bring in excess outdoor air when the indoor and outdoor humidity ratios were essentially equal. Adding a small tolerance makes the control more consistent.
• Diffs expected for UnitarySystem_FurnaceWithDXSystemRHControl.idf and others with this control.

Explanation of Diffs

These test files have OA controller "High Humidity Control" = Yes.
FurnaceWithDXSystemRHControl, HeatPumpAirToAirWithRHControl, HPAirToAir_wSolarCollectorHWCoil, HP_wICSSolarCollector, HVACStandAloneERV_Economizer, UnitarySystem_FurnaceWithDXSystemRHControl, and UnitarySystem_WaterCoils_wMultiSpeedFan. Six of these are showing small or large eso diffs, as expected.

Looking at UnitarySystem_FurnaceWithDXSystemRHControl, for example. The following chart shows before and after, zone humidity ratio, OA humidity ratio, and "Air System Outdoor Air High Humidity Control Status". See how the high humidity control was kicking on randomly on the winter design day (left end of chart). After the fix, it stays off.

Pull Request Author

Add to this list or remove from it as applicable. This is a simple templated set of guidelines.

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• Perform a Code Review on GitHub
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[mjwitte]

Using new approach for global constants - just declare it right in the header. Better for compiler optimization instead of using extern. Tempted to change all of these here, but don't want to muddy the waters.

[mjwitte]

Require delta humrat to be > SmallHumRatDiff to activate high humidity flow rate.

[mjwitte]

New unit test with 4 cases.

[mitchute]

@mjwitte this looks good. It looks like CI is having issues again, so I'll merge this once that has a chance to get worked out.

[mitchute]

Merging. Some of the expected-diff files have tanks, so make sure to pull develop into #7541 before reviewing.