Fix various useful clang-tidy warnings

* bugprone-branch-clone
* bugprone-copy-constructor-init
* bugprone-empty-catch
* bugprone-sizeof-expression
* bugprone-switch-missing-default-case
* bugprone-unused-local-non-trivial-variable
* clang-analyzer-core.uninitialized.Assign
* clang-analyzer-cplusplus.Move
* clang-analyzer-optin.cplusplus.VirtualCall
* modernize-loop-convert
* modernize-raw-string-literal
* modernize-use-equals-default
* modernize-use-override
* modernize-use-using
* performance-avoid-endl
* performance-inefficient-string-concatenation
* performance-inefficient-vector-operation
* performance-noexcept-move-constructor
* performance-unnecessary-value-param (and improve generator example)
* readability-duplicate-include
* readability-inconsistent-declaration-parameter-name
* readability-non-const-parameter
* readability-redundant-casting
* readability-redundant-member-init
* readability-redundant-smartptr-get
* readability-static-accessed-through-instance
* unused variable in amalgamted tests

src/catch2/internal/catch_stringref.hpp

@@ -97,8 +97,8 @@ namespace Catch {
         constexpr const_iterator end() const { return m_start + m_size; }
 
 
-        friend std::string& operator += (std::string& lhs, StringRef sr);
-        friend std::ostream& operator << (std::ostream& os, StringRef sr);
+        friend std::string& operator += (std::string& lhs, StringRef rhs);
+        friend std::ostream& operator << (std::ostream& os, StringRef str);
         friend std::string operator+(StringRef lhs, StringRef rhs);
 
         /**