Move TopUp() responsibility from the wallet class to each scriptpubkeyman.
So each spkm can decide to call it or not after perform the basic checks
for the new destination request.
Reason:
We were calling it twice in the following flows for descriptor wallets:
A) CWallet::GetNewDestination:
1) Calls spk_man->TopUp()
2) Calls spk_man->GetNewDestination() --> which, after the basic script checks, calls TopUp() again.
B) CWallet::GetReservedDestination:
1) Calls spk_man->TopUp()
2) Calls spk_man->GetReservedDestination() --> which calls to GetNewDestination (which calls to TopUp again).
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