Merge bitcoin/bitcoin#33192: refactor: unify container presence checks

d9319b06cf refactor: unify container presence checks - non-trivial counts (Lőrinc)
039307554e refactor: unify container presence checks - trivial counts (Lőrinc)
8bb9219b63 refactor: unify container presence checks - find (Lőrinc)

Pull request description:

  ### Summary
  Instead of counting occurrences in sets and maps, the C++20 `::contains` method expresses the intent unambiguously and can return early on first encounter.

  ### Context
  Applied clang‑tidy's [readability‑container‑contains](https://clang.llvm.org/extra/clang-tidy/checks/readability/container-contains.html) check, though many cases required manual changes since tidy couldn't fix them automatically.

  ### Changes
  The changes made here were:

  | From                   | To               |
  |------------------------|------------------|
  | `m.find(k) == m.end()` | `!m.contains(k)` |
  | `m.find(k) != m.end()` | `m.contains(k)`  |
  | `m.count(k)`           | `m.contains(k)`  |
  | `!m.count(k)`          | `!m.contains(k)` |
  | `m.count(k) == 0`      | `!m.contains(k)` |
  | `m.count(k) != 1`      | `!m.contains(k)` |
  | `m.count(k) == 1`      | `m.contains(k)`  |
  | `m.count(k) < 1`       | `!m.contains(k)`  |
  | `m.count(k) > 0`       | `m.contains(k)`  |
  | `m.count(k) != 0`      | `m.contains(k)`  |

  > Note that `== 1`/`!= 1`/`< 1` only apply to simple [maps](https://en.cppreference.com/w/cpp/container/map/contains)/[sets](https://en.cppreference.com/w/cpp/container/set/contains) and had to be changed manually.

  There are many other cases that could have been changed, but we've reverted most of those to reduce conflict with other open PRs.

  -----

  <details>
  <summary>clang-tidy command on Mac</summary>

  ```bash
  rm -rfd build && \
  cmake -B build \
    -DCMAKE_C_COMPILER="$(brew --prefix llvm)/bin/clang" \
    -DCMAKE_CXX_COMPILER="$(brew --prefix llvm)/bin/clang++" \
    -DCMAKE_OSX_SYSROOT="$(xcrun --show-sdk-path)" \
    -DCMAKE_C_FLAGS="-target arm64-apple-macos11" \
    -DCMAKE_CXX_FLAGS="-target arm64-apple-macos11" \
    -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DBUILD_BENCH=ON -DBUILD_FUZZ_BINARY=ON -DBUILD_FOR_FUZZING=ON

   "$(brew --prefix llvm)/bin/run-clang-tidy" -quiet -p build -j$(nproc) -checks='-*,readability-container-contains' | grep -v 'clang-tidy'
  ```

  </details>

  Note: this is a take 2 of https://github.com/bitcoin/bitcoin/pull/33094 with fewer contentious changes.

ACKs for top commit:
  optout21:
    reACK d9319b06cf
  sedited:
    ACK d9319b06cf
  janb84:
    re ACK d9319b06cf
  pablomartin4btc:
    re-ACK d9319b06cf
  ryanofsky:
    Code review ACK d9319b06cf. I manually reviewed the full change, and it seems there are a lot of positive comments about this and no more very significant conflicts, so I will merge it shortly.

Tree-SHA512: e4415221676cfb88413ccc446e5f4369df7a55b6642347277667b973f515c3c8ee5bfa9ee0022479c8de945c89fbc9ff61bd8ba086e70f30298cbc1762610fe1

src/qt/walletframe.cpp

@@ -70,7 +70,7 @@ bool WalletFrame::addView(WalletView* walletView)
 {
     if (!clientModel) return false;
 
-    if (mapWalletViews.count(walletView->getWalletModel()) > 0) return false;
+    if (mapWalletViews.contains(walletView->getWalletModel())) return false;
 
     walletView->setClientModel(clientModel);
     walletView->showOutOfSyncWarning(bOutOfSync);
@@ -90,7 +90,7 @@ bool WalletFrame::addView(WalletView* walletView)
 
 void WalletFrame::setCurrentWallet(WalletModel* wallet_model)
 {
-    if (mapWalletViews.count(wallet_model) == 0) return;
+    if (!mapWalletViews.contains(wallet_model)) return;
 
     // Stop the effect of hidden widgets on the size hint of the shown one in QStackedWidget.
     WalletView* view_about_to_hide = currentWalletView();
@@ -116,7 +116,7 @@ void WalletFrame::setCurrentWallet(WalletModel* wallet_model)
 
 void WalletFrame::removeWallet(WalletModel* wallet_model)
 {
-    if (mapWalletViews.count(wallet_model) == 0) return;
+    if (!mapWalletViews.contains(wallet_model)) return;
 
     WalletView *walletView = mapWalletViews.take(wallet_model);
     walletStack->removeWidget(walletView);