misc: fix issues pointed out by msvc (#7316)

* do not move constant variables

* applet_manager: avoid possible use after move

* use constant references where pointed out by msvc

* extra_hid: initialize response

* ValidateSaveState: passing slot separately is not necessary

* common: mark HashCombine as nodiscard

* cityhash: remove use of using namespace std

* Prefix all size_t with std::

done automatically by executing regex replace `([^:0-9a-zA-Z_])size_t([^0-9a-zA-Z_])` -> `$1std::size_t$2`
based on 7d8f115

* shared_memory.cpp: fix log error format

* fix compiling with pch off

src/citra/config.cpp

@@ -236,7 +236,7 @@ void Config::ReadValues() {
         std::string offset_string =
             sdl2_config->GetString("System", "init_time_offset", default_init_time_offset);
 
-        size_t sep_index = offset_string.find(' ');
+        std::size_t sep_index = offset_string.find(' ');
 
         if (sep_index == std::string::npos) {
             LOG_ERROR(Config, "Failed to parse init_time_offset. Using 0 00:00:00");