Address inconsistencies in the `traefik-forward-auth` chart

[Cole Arendt]

The traefik-forward-auth chart has some inconsistencies that we should back out. However, some are breaking changes, so should be done carefully:

• serviceAnnotations vs. service.annotations
• Not using helpers for selectorLabels, labels or fullName (the latter has a risk for long names)
• Other config options missing that are normally in my charts...