[chore] Refactor STTextViewController to reduce duplication

[austincondiff]

Description

Fixed a few UI bugs by reducing overlap between loadView and reloadUI and calling reloadUI from loadView. These include...

• There were some areas where the theme background was not getting applied.
• The currently selected line was not getting a background in the ruler view until changing a setting which called reloadUI.

Now loadView calls reloadUI which allows us to reduce code duplication

Related Issues

• n/a

Checklist

• I read and understood the contributing guide as well as the code of conduct
• The issues this PR addresses are related to each other
• My changes generate no new warnings
• My code builds and runs on my machine
• My changes are all related to the related issue above
• I documented my code

Screenshots

n/a