6e77a7b65cda1b46ce42f0c99ca91562255aeb28 keypool: Add comment about TopUp and when to use it (Andrew Chow)
ea50e34b287e0da0806c1116bb55ade730e8ff6c keypool: Move opportunistic TopUps from LegacyScriptPubKeyMan to CWallet and ReserveDestination (Andrew Chow)
bb2c8ce23c9d7ba8d0e5538243e07218443c85b4 keypool: Remove superfluous topup from CWallet::GetNewChangeDestination (Andrew Chow)
Pull request description:
* The `TopUp()` in `CWallet::GetNewChangeDestination` is unnecessary as currently m_spk_man calls TopUp further down the call stack inside LegacyScriptPubKeyMan::ReserveKeyFromKeyPool (called by LegacyScriptPubKeyMan::GetReservedDestination). This also lets us prepare for future changes with multiple ScriptPubKeyMans in the wallet.
* An opportunistic `TopUp()` is moved from `LegacyScriptPubKeyMan::GetNewDestination` to `CWallet::GetNewDestination`.
* Another opportunistic `TopUp()` is moved from `LegacyScriptPubKeyMan::ReserveKeyFromKeyPool`
Moving opportunistic TopUps ensures that ScriptPubKeyMans will always be topped up before requesting Destinations from them as we cannot always rely on future ScriptPubKeyMan implementaions topping up internally.
See also: https://github.com/bitcoin/bitcoin/pull/17373#discussion_r348598174
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Backport of Core PR17537