Set active/initial tab number through rules editor

[slactasha]

What's the problem this feature will solve? It would convenient to have the option in the Rules editor to set the initial or active tab on the tab container based on a PV value or a macro.

Describe the solution you'd like E.g. we have some common pages we launch from LCLSHOME with two tabs - one for the superconducting linac and one for the copper linac. The source (NC/SC) is propagated as a macro, so it would be ideal to automatically change the tab on the common page based on that macro value. Similar cases exist where the information is in an enumerated PV instead of a macro.

Additional context This is kind of an addition to the fix applied in #764