Merge #20566: refactor: Use C++17 std::array where possible

fac7ab1 refactor: Use C++17 std::array where possible (MarcoFalke)

Pull request description:

  Using the C++11 std::array with explicit template parameters is problematic because overshooting the size will fill the memory with default constructed types.

  For example,

  ```cpp
  #include <array>
  #include <iostream>

  int main()
  {
      std::array<int, 3> a{1, 2};
      for (const auto& i : a) {
          std::cout << i << std::endl;  // prints "1 2 0"
      }
  }
  ```

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Tree-SHA512: ef7e872340226e0d6160e6fd66c6ca78b2ef9c245fa0ab27fe4777aac9fba8d5aaa154da3d27b65dec39a6a63d07f1063c3a8ffb667a98ab137756a1a0af2656

Author: MarcoFalke

src/qt/sendcoinsdialog.cpp

@@ -35,7 +35,7 @@
 #include <QSettings>
 #include <QTextDocument>
 
-static const std::array<int, 9> confTargets = { {2, 4, 6, 12, 24, 48, 144, 504, 1008} };
+static constexpr std::array confTargets{2, 4, 6, 12, 24, 48, 144, 504, 1008};
 int getConfTargetForIndex(int index) {
     if (index+1 > static_cast<int>(confTargets.size())) {
         return confTargets.back();

src/wallet/walletutil.cpp

@@ -91,7 +91,7 @@ bool IsFeatureSupported(int wallet_version, int feature_version)
 
 WalletFeature GetClosestWalletFeature(int version)
 {
-    const std::array<WalletFeature, 8> wallet_features{{FEATURE_LATEST, FEATURE_PRE_SPLIT_KEYPOOL, FEATURE_NO_DEFAULT_KEY, FEATURE_HD_SPLIT, FEATURE_HD, FEATURE_COMPRPUBKEY, FEATURE_WALLETCRYPT, FEATURE_BASE}};
+    static constexpr std::array wallet_features{FEATURE_LATEST, FEATURE_PRE_SPLIT_KEYPOOL, FEATURE_NO_DEFAULT_KEY, FEATURE_HD_SPLIT, FEATURE_HD, FEATURE_COMPRPUBKEY, FEATURE_WALLETCRYPT, FEATURE_BASE};
     for (const WalletFeature& wf : wallet_features) {
         if (version >= wf) return wf;
     }