Add lint warning for AppCtx

[LouisCAD]

A persistent lint warning should be present for any Context.injectAsAppCtx() usage since it's potentially unsafe to use. This should escalate to fatal if directly called with a subclass of the types know to Context.canLeakMemory().

There could also lint warnings when using appCtx to get resources that are commonly invalidated with common configuration changes (dimensions with screen rotation for example) or which rely on theme.