[clang] [clang-tools-extra] [clang-tidy] Add readability-avoid-default-lambda-capture (PR #160150)

[JJ Marr via cfe-commits]

================
@@ -0,0 +1,57 @@
+.. title:: clang-tidy - readability-avoid-default-lambda-capture
+
+readability-avoid-default-lambda-capture
+========================================
+
+Warns on default lambda captures (e.g. ``[&](){ ... }``, ``[=](){ ... }``).
+  
+Captures can lead to subtle bugs including dangling references and unnecessary
+copies. Writing out the name of the variables being captured reminds programmers
+and reviewers to know what is being captured. And knowing is half the battle.
+
+This check does not lint for variable-length array (VLA) captures. VLAs are not
+ISO C++, and it is impossible to explicitly capture them as the syntax for doing
+so does not exist.
+
+Coding guidelines that recommend against defaulted lambda captures include:
+
+* Item 31 of Effective Modern C++ by Scott Meyers
+
+Example
+-------
+
+.. code-block:: c++
+
+  #include <iostream>
+
+  class Widget {
+    std::vector<std::function<void(int)>> callbacks;
+    int                                   widgetId;
+    void addCallback(int factoryId) {
+      callbacks.emplace_back(
+        [&](){
+          std::cout << "Widget " << widgetId << " made in factory " << factoryId;
+        }
+      );
+    }
+  }
----------------
jjmarr-amd wrote:

I made up the example myself.

https://github.com/llvm/llvm-project/pull/160150