Update Activity tab and Single Activity screen

With grouping internal transactions in Activities [1], there are some UI and UX improvements that we might want to consider, since there are now "standalone" and "grouped" transactions/activities:

- [ ] The UI itself for the Activity tab [2].
- [ ] Keeping them all of them expanded all the time might be a lot of noise? But tapping to expand means we need to add an additional placeholder row for the "main" transaction, or a button/toolbar to expand/collapse? Do we need a pseudo parent for the group?
- [ ] When we tap on a group, what happens?
- [ ] When we tap on a row in the group, what happens?
- [ ] Also, recent transactions in token view, the screen displayed after tapping on a token. How do we display them and what do we display? The latter — do we show a group if it contains transactions that involve this token?

[1] The "internal" transactions are all token transfers, for now at least
[2] Screenshot: