Consistency in StatusBar UI

Suggestions by @redmunds on https://github.com/adobe/brackets/issues/8150

Add tooltip and underline text when hovering over the OVR/INS element. Change cursor to hand when hovering over the Lint icon.
I think it would be more explanatory (and also simplify the code) to have a single tool tip that says something like:

"Click to toggle cursor between Insert (INS) and Overwrite (OVR) modes"