[SmartHolder] fix(clang-tidy): apply clang-tidy performance fixes (#3048)

* Apply clang-tidy performance fixes

* Fix bug introduced by double insert

* Revert all non-smart-holder changes

Author: Skylion007

include/pybind11/detail/smart_holder_type_casters.h

@@ -79,7 +79,7 @@ class modified_type_caster_generic_load_impl {
             }
             // type_caster_generic::load_value END
         }
-        loaded_v_h = std::move(v_h);
+        loaded_v_h = v_h;
         loaded_v_h.type = typeinfo;
     }
 

include/pybind11/trampoline_self_life_support.h

@@ -53,7 +53,7 @@ struct trampoline_self_life_support {
     // For the next two, the default implementations generate undefined behavior (ASAN failures
     // manually verified). The reason is that v_h needs to be kept default-initialized.
     trampoline_self_life_support(const trampoline_self_life_support &) {}
-    trampoline_self_life_support(trampoline_self_life_support &&) {}
+    trampoline_self_life_support(trampoline_self_life_support &&) noexcept {}
 
     // These should never be needed (please provide test cases if you think they are).
     trampoline_self_life_support &operator=(const trampoline_self_life_support &) = delete;