Extend MODFLOW 6's TVK Package Capabilities to Include Varying Anisotropy Angles

[Callum-AG]

Is your feature request related to a problem? Please describe.
Consider a model with mining in which the "angles" parameter is used in NPF to orient the vertical conductivity axis in the appropriate direction. In this model, mining activity would transform the properties of the material in certain cells to those of spoil or tailings using TVK, however the anisotropy angles provided in the NPF package would no longer be appropriate for modelling the new material as the structure of the porous matrix of the host layer would be disturbed by mining.

Describe the solution you'd like
Ability to specify angle1, angle2 and angle3 as tvksetting values for the TVK package.