Merge bitcoin-core/gui#686: clang-tidy: Force checks for headers in src/qt

7b7cd11244 clang-tidy, qt: Force checks for headers in `src/qt` (Hennadii Stepanov)
69eacf2c5e clang-tidy, qt: Fix `modernize-use-default-member-init` in headers (Hennadii Stepanov)

Pull request description:

  This PR split from bitcoin/bitcoin#26705 and contains only changes in `src/qt`.

  Effectively, it fixes the clang-tidy's `modernize-use-default-member-init` errors, and forces clang-tidy checks for all headers in the `src/qt` directory.

ACKs for top commit:
  jarolrod:
    ACK 7b7cd11244

Tree-SHA512: 79525bb0f31ae7cad88c781e55091a21467c0485ddc1ed03ad62e051480fda3b3710619ea11af480437edba3c6e038f7c40edc6b373e3a37408c006d11b34686

src/qt/peertablemodel.cpp

@@ -14,10 +14,9 @@
 #include <QList>
 #include <QTimer>
 
-PeerTableModel::PeerTableModel(interfaces::Node& node, QObject* parent) :
-    QAbstractTableModel(parent),
-    m_node(node),
-    timer(nullptr)
+PeerTableModel::PeerTableModel(interfaces::Node& node, QObject* parent)
+    : QAbstractTableModel(parent),
+      m_node(node)
 {
     // set up timer for auto refresh
     timer = new QTimer(this);