Merge bitcoin-core/gui#441: Add Create Unsigned button to SendConfirmationDialog

742918c8ef qt: hide Create Unsigned button behind an expert mode option (Andrew Chow)
5c3b800acd qt: Add Create Unsigned button to SendConfirmationDialog (Andrew Chow)

Pull request description:

  Instead of having different buttons or changing button behavior for making a PSBT, just have SendConfirmationDialog return whether the user wants a PSBT or a broadcasted transaction. Since this dialog is used by both the bumpFeeAction and the SendCoinsDialog, changes to both to support the different behavior is needed. They will check the return value of the SendConfirmationDialog for whether a PSBT needs to be created instead of checking whether private keys are disabled.

  Strings used in this dialog are being slightly modified to work with both private keys enabled and disabled wallets.

  Moved from https://github.com/bitcoin/bitcoin/pull/18789

ACKs for top commit:
  jarolrod:
    ACK 742918c
  ryanofsky:
    Code review ACK 742918c8ef. Just suggested changes since last review. Looks great!
  hebasto:
    ACK 742918c8ef, tested on Linux Mint 20.2 (Qt 5.12.8).

Tree-SHA512: dd29f4364c7b4f15befe8fe63257b26187918786b005e0f8336183270b1a162680b93f6ced60f0285c6e607c084cc0d24950fc68a8f9c056521ede614041be66

src/qt/optionsmodel.h

@@ -69,6 +69,7 @@ public:
         SpendZeroConfChange,    // bool
         Listen,                 // bool
         Server,                 // bool
+        EnablePSBTControls,     // bool
         OptionIDRowCount,
     };
 
@@ -90,6 +91,7 @@ public:
     bool getUseEmbeddedMonospacedFont() const { return m_use_embedded_monospaced_font; }
     bool getCoinControlFeatures() const { return fCoinControlFeatures; }
     bool getSubFeeFromAmount() const { return m_sub_fee_from_amount; }
+    bool getEnablePSBTControls() const { return m_enable_psbt_controls; }
     const QString& getOverriddenByCommandLine() { return strOverriddenByCommandLine; }
 
     /* Explicit setters */
@@ -115,6 +117,7 @@ private:
     bool m_use_embedded_monospaced_font;
     bool fCoinControlFeatures;
     bool m_sub_fee_from_amount;
+    bool m_enable_psbt_controls;
     /* settings that were overridden by command-line */
     QString strOverriddenByCommandLine;