refactor: Add simple clang-tidy readability checks (#6556)

This change enables the following clang-tidy checks:
-  readability-avoid-nested-conditional-operator,
-  readability-avoid-return-with-void-value,
-  readability-braces-around-statements,
-  readability-const-return-type,
-  readability-container-contains,
-  readability-container-size-empty,
-  readability-else-after-return,
-  readability-make-member-function-const,
-  readability-redundant-casting,
-  readability-redundant-inline-specifier,
-  readability-redundant-member-init,
-  readability-redundant-string-init,
-  readability-reference-to-constructed-temporary,
-  readability-static-definition

src/test/peerfinder/Livecache_test.cpp

@@ -30,7 +30,7 @@ public:
 
     // Add the address as an endpoint
     template <class C>
-    inline void
+    void
     add(beast::IP::Endpoint ep, C& c, std::uint32_t hops = 0)
     {
         Endpoint cep{ep, hops};