Replace updateCurrentAccount() with refreshSession()

[gaearon]

Extracted-ish from #3728.

When you change email, handle, emailConfirmed, or other fields present in the session object, it would previously get updated in local state. However, the underlying agent.session was not updated. So there could be cases where an agent.session would reflect back into the app state and clobber it (despite being out of date).

Ideally the agent should take care of updating its own agent.session (and emitting an update event) when we call API methods that are known to mutate email, handle, etc. Until it does that, we're going to explicitly call agent.resumeSession in those places to force a session refetch which will go through the usual mechanism. We don't need any special state handling because it'll be handled in our existing handler for the update event.

Since we don't need any special handling for the state, and because most likely this logic will later move into the agent itself anyway, I ripped updateCurrentAccount out of the session API interface.

Test Plan

Changed email, verified email, changed handle, changed 2FA setting. Everything seems to be reflected in the UI.

These "feel" a bit slower (due to a serial request) but we should really fix that in the agent itself. I think it's OK. We can also add better pending states (e.g. disable the 2FA switch while toggling it), but I didn't do it in this PR.

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[github-actions]

Old size	New size	Diff
6.89 MB	6.89 MB	-422 B (-0.01%)

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