[MaterialSwitch] Support for processing state

Is your feature request related to a problem? Please describe.

Support processing state drawable for thumb as suggested in material docs. This helps with business logic where a request can't be processed immediately and has some user noticeable latency like network requests.

Describe the solution you'd like

API to specify processing state drawable (to be drawn over thumb). It would be nice to support default processing drawable.
API to indicate processing state when calling setChecked for both on and off states

setChecked(true, true) -> On state and loading
setChecked(true, false) -> On state
setChecked(false, true) -> Off state and loading
setChecked(false, false) -> Off state

Describe alternatives you've considered

Additional context

https://user-images.githubusercontent.com/1020585/234715458-f114e73e-0d1a-41c8-93d8-01247c6ae01a.mov

We also happily accept pull requests.

Inizia dal componente MaterialSwitch e dal suo punto di ingresso setChecked esistente, quindi segui come vengono gestiti il drawable del thumb e le modifiche allo stato checked. Definisci il drawable di elaborazione e il comportamento di caricamento per le quattro combinazioni di setChecked descritte nell’issue, preservando le normali visualizzazioni di attivato e disattivato.