Add enableShiftScroll setting and related functionality

[larry-xue]

This pr introduces a new setting, enableShiftScroll, that allows you to control the behavior of mouse wheel tab switching.

Changes include:

• Added enableShiftScroll to SettingsRec in WtProgram/Settings.fs, defaulting to true.
• Updated settings serialization in WtProgram/Settings.fs to handle the new setting.
• Modified WtProgram/GroupPlugins/MouseScrollPlugin.fs to read the enableShiftScroll setting and adjust its behavior - accordingly.
• Added a checkbox in the Behavior settings view (WtProgram/ManagerViewService/Views/BehaviorView.fs) to allow you to toggle - this new setting. The checkbox label will be generated as "Enable Shift Scroll".

[larry-xue]

Sorry for the multiple pull/close actions. I noticed some problems in my initial commits that require correction.