[rpc] fundrawtransaction, walletcreatefundedpsbt lock manually selected coins

Previously only automatically selected coins were locked when lockUnspents is set.
It now also locks selected coins.

doc/release-notes-18244.md

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+Updated RPCs
+------------
+
+- `fundrawtransaction` and `walletcreatefundedpsbt` when used with the `lockUnspents`
+   argument now lock manually selected coins, in addition to automatically selected
+   coins. Note that locked coins are never used in automatic coin selection, but
+   can still be manually selected.