Port yuzu-emu/yuzu#2529: "yuzu/bootmanager: Minor interface tid… (#4794)

* yuzu/bootmanager: Remove unnecessary pointer casts

We can just invoke these functions by qualifying the object name before
the function.

* yuzu/bootmanager: unsigned -> u32

Same thing (for platforms we support), less reading.

* yuzu/bootmanager: Default EmuThread's destructor in the cpp file

This class contains non-trivial members, so we should default the
destructor's definition within the cpp file.

* yuzu/bootmanager: Treat the resolution factor as a u32

Treating it as a u16 can result in a sign-conversion warning when
performing arithmetic with it, as u16 promotes to an int when aritmetic
is performed on it, not unsigned int.

This also makes the interface more uniform, as the layout interface now
operates on u32 across the board.

* yuzu/bootmanager: Log out screenshot destination path

We can make this message more meaningful by indicating the location the
screenshot has been saved to. We can also log out whenever a screenshot
could not be saved (e.g. due to filesystem permissions or some other
reason).

* Fix compilation

src/core/frontend/emu_window.h

@@ -146,8 +146,7 @@ private:
      * For the request to be honored, EmuWindow implementations will usually reimplement this
      * function.
      */
-    virtual void OnMinimalClientAreaChangeRequest(
-        const std::pair<unsigned, unsigned>& minimal_size) {
+    virtual void OnMinimalClientAreaChangeRequest(std::pair<u32, u32> minimal_size) {
         // By default, ignore this request and do nothing.
     }