fix(wallet): do check_wallet_descriptor when creating and loading

[ValuedMammal]

Do check_wallet_descriptor for both external and internal descriptors when creating a wallet, and as a defensive measure also perform the check on the descriptors loaded from a changeset.

fixes #1557

Checklists

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• I've signed all my commits
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• I ran cargo fmt and cargo clippy before committing

[notmandatory]

ACK 5aecf4d