- create new dedicated (asset) token selector component
- integrate it into `SwapInputPanel` and `SwapModal`
- add respective SB page and QML tests suite
Fixes#14783
- new panel created: `SwapInputPanel`
- some cleanups to the needed stores
- created a SB page demonstrating the use of 2 panels and the
`SwapExchangeButton`
- created QML tests
Fixes#14781