qt: Add BitcoinUnits::formatWithPrivacy() function

Summary:
> This PR allows to hide/reveal values on the Overviewpage by checking/unchecking Menu->Settings-> Mask Values

This is a backport of [[bitcoin/bitcoin#16432 | core#16432]] [1/2]
bitcoin/bitcoin@73d8ef7

Test Plan: `ninja all check-all`

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D9919

src/qt/bitcoinunits.cpp

@@ -10,6 +10,8 @@
 
 #include <QStringList>
 
+#include <cassert>
+
 // clang-format off
 using unitNameMap =
     std::map<
@@ -104,7 +106,7 @@ int BitcoinUnits::decimals(int unit) {
 }
 
 QString BitcoinUnits::format(int unit, const Amount nIn, bool fPlus,
-                             SeparatorStyle separators) {
+                             SeparatorStyle separators, bool justify) {
     // Note: not using straight sprintf here because we do NOT want
     // localized number formatting.
     if (!valid(unit)) {
@@ -117,6 +119,9 @@ QString BitcoinUnits::format(int unit, const Amount nIn, bool fPlus,
     qint64 n_abs = (n > 0 ? n : -n);
     qint64 quotient = n_abs / coin;
     QString quotient_str = QString::number(quotient);
+    if (justify) {
+        quotient_str = quotient_str.rightJustified(16 - num_decimals, ' ');
+    }
 
     // Use SI-style thin space separators as these are locale independent and
     // can't be confused with the decimal marker.
@@ -167,6 +172,20 @@ QString BitcoinUnits::formatHtmlWithUnit(int unit, const Amount amount,
     return QString("<span style='white-space: nowrap;'>%1</span>").arg(str);
 }
 
+QString BitcoinUnits::formatWithPrivacy(int unit, const Amount &amount,
+                                        SeparatorStyle separators,
+                                        bool privacy) {
+    assert(amount >= Amount::zero());
+    QString value;
+    if (privacy) {
+        value = format(unit, Amount::zero(), false, separators, true)
+                    .replace('0', '#');
+    } else {
+        value = format(unit, amount, false, separators, true);
+    }
+    return value + QString(" ") + shortName(unit);
+}
+
 bool BitcoinUnits::parse(int unit, const QString &value, Amount *val_out) {
     if (!valid(unit) || value.isEmpty()) {
         // Refuse to parse invalid unit or empty string

src/qt/bitcoinunits.h

@@ -63,7 +63,8 @@ class BitcoinUnits : public QAbstractListModel {
     static int decimals(int unit);
     //! Format as string
     static QString format(int unit, const Amount amount, bool plussign = false,
-                          SeparatorStyle separators = separatorStandard);
+                          SeparatorStyle separators = separatorStandard,
+                          bool justify = false);
     //! Format as string (with unit)
     static QString
     formatWithUnit(int unit, const Amount amount, bool plussign = false,
@@ -72,6 +73,10 @@ class BitcoinUnits : public QAbstractListModel {
     static QString
     formatHtmlWithUnit(int unit, const Amount amount, bool plussign = false,
                        SeparatorStyle separators = separatorStandard);
+    //! Format as string (with unit) of fixed length to preserve privacy, if it
+    //! is set.
+    static QString formatWithPrivacy(int unit, const Amount &amount,
+                                     SeparatorStyle separators, bool privacy);
     //! Parse string to coin amount
     static bool parse(int unit, const QString &value, Amount *val_out);
     //! Gets title for amount column including current display unit if