Display current Node Activity to make it's behavior more clear

[brusherru]

Rationale

When the Node is synced and PoS data is created, then it is tough to understand if is everything going well, or not. So Users wait for a long time, and some of them then find out that they don't get rewards, and ask why...

Recently a new API was introduced in go-spacemesh, that provides a Stream of Node Events: spacemeshos/go-spacemesh#4635

Smapp should subscribe to this API, and display on the smesher screen:

• what is happening now (current event)
• what will happen next (expected next event? Mb we don't need it and better document the whole lifecycle somewhere)
• in case of failure — show the error instead of the current activity

User story

• I open Smapp
• Set up smeshing
• I observe Node current activity on Smesher screen: InitStart -> InitComplete -> PoetWait -> PoetWaitEnd -> PostStart -> ...
• If something failed — show the red bulb and red error message instead of the current activity