AD: merge more of `TwrInfl` and `TwrInflArray` routines

[bjonkman]

Feature or improvement description This PR merges more parts of the TwrInfl and TwrInflArray, which are basically two copies of the tower influence calculations, one for the BEMT module and the other for FVW.

This merger introduces a few changes to how the code checks that the tower influence should be applied:

1. BEMT now turns off the tower influence if the tower clearance is more than 20 times the tower diameter.
2. BEMT now turns off the tower influence if the tower clearance is less than 0.01 times the tower diameter.
3. BEMT now limits the tower shadow influence to no more than -1/2 the wind speed at the tower.
4. FVW now limits the tower shadow influence to no more than -1/2 the wind speed at the tower for all tower shadow models. It previously was applying this limit only to the Eames model.

Note: this PR also fixes an issue where there were some uninitialized variables in the FVW tower influence calculations if the tower clearance was > 20 TowerDiam or < 0.01 TowerDiam.

Impacted areas of the software AeroDyn (AD15)

Test results, if applicable Tests with any of the properties listed above may be affected. In general, we wouldn't expect those conditions to apply for normal BEMT simulations. However, the OpenFAST reg-test does have AOC models with tower-diameters of 0.06 m, so the new checks effectively turn off all tower influence calculations in those cases.

A few other cases fail, but those small differences are likely due to optimizations.