Part of T80730

Some files needed to be changed manually.

curve_assign_shapekey: 1) Changed call to space.overlay.show_curve_handles to space.overlay.display_handle as per the API change in 2.90  2) Removed redundant call to shader.bind 3) Removed redundant modal handlers in ModalMarkSegStartOp

curve_assign_shapekey: Fix for condition where target has existing shapekeys and basis shape key is different than curve

curve_assign_shapekey: 1) Passed target & shape key objects as params to main function 2) Fix to retain first key name, if target already has shape keys

curve_assign_shapekey: Separate list for Vertex Alignment Criteria with only min and max of each axis. Other values from matchList (like Vertex Count) are not relevant for Vertex Alignment Criteria.

curve_assign_shapekey: 1) Moved the add-on panel to Sidebar -> Edit tab 2) Made the panel tab user configurable 3) Changed the license type to GPL3

curve_assign_shapekey: 1) moved UI and registration to bottom of the script 2) trimmed trailing whitespace 3) 2 lines between classes: T62799