[backport#17369] Refactor: Move encryption code between KeyMan and Wallet

Summary:
7cecf10ac32af0fca206ac5f24f482bdec88cb7d Replace LegacyScriptPubKeyMan::IsCrypted with LegacyScriptPubKeyMan::HasEncryptionKeys (Andrew Chow)
bf6417142f36a2f75b3a11368bd73fe788ae1ccb Remove SetCrypted() and fUseCrypto; Change IsCrypted()'s implementation (Andrew Chow)
77a777118eaf78f10a439810d1c08d510a539aa0 Rename EncryptKeys to Encrypt and pass in the encrypted batch to use (Andrew Chow)
35f962fcf0d5107ae6a3a9348e249a9b18ff7106 Clear mapKeys before encrypting (Andrew Chow)
14b5efd66ff0afbf3bf9158a724534a9090fc7fc Move fDecryptionThoroughlyChecked from CWallet to LegacyScriptPubKeyMan (Andrew Chow)
97c0374a46943b2ed38ea24eeeff1f1568dd55b3 Move Unlock implementation to LegacyScriptPubKeyMan (Andrew Chow)
e576b135d6451101d6a8219f55d80aefa216dc38 Replace LegacyScriptPubKeyMan::vMasterKey with GetDecryptionKey() (Andrew Chow)
fd9d6eebc1eabb4675a118d19d38283da2dead39 Add GetEncryptionKey() and HasEncryptionKeys() to WalletStorage (Andrew Chow)

Pull request description:

Let wallet class handle locked/unlocked status and master key, and let keyman
handle encrypting its data and determining whether there is encrypted data.

There should be no change in behavior, but state is tracked differently. The
fUseCrypto atomic bool is eliminated and replaced with equivalent
HasEncryptionKeys checks.

Split from #17261

Depends on D7697

Backport of Core PR17369

Test Plan:

ninja check check-functional

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7698