feat: cache .well-known data

[TheOneWithTheBraid]

• BREAKING: remove DiscoveryInformation from the checkHomeserver response tuple
• BREAKING: create DatabaseApi.storeWellKnown method
• BREAKING: create DatabaseApi.getWellKnown method
• add new getter Client.wellKnown containing cached DiscoveryInformation
• override Client.homeserver to invalidate Client.wellKnown in case the domain changed
• override Client.getWellknown to cache the resolved DiscoveryInformation
• add tests for well-known cache

Fixes: https://github.com/famedly/matrix-dart-sdk/issues/1865

[TheOneWithTheBraid]

Ping @krille-chan !

[TheOneWithTheBraid]

Poke @nico-famedly !