[common] Switch to boost::unordered_flat containers (#4326)

Replaces all instances of ankerl's unordered map/set with boost's
`unordered_flat_*` classes. This uses std::hash since boost::hash is
actually a lot slower.

Also adds an abstraction layer in `Common` so future changes are quicker
and easier.

Other implementation details:
- ankerl provided hash specializations for tuple and pair, so those were
  ported here
- std::erase_if doesn't work on boost, so just used the ADL'd erase_if

This should be about equal or superior performance as unordered_dense for everything except iteration.

Signed-off-by: crueter <crueter@eden-emu.dev>

- [x] I have read and followed the [Contribution Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/CONTRIBUTING.md#code-contributions).
- [x] I have read and followed the [AI Policy](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/AI.md)
- [x] I have read and followed the [Coding Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/Coding.md) to the best of my ability.

-------------------

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4326
Reviewed-by: Lizzie and Samuel <lizzie@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/hid_core/frontend/emulated_console.h

@@ -11,7 +11,7 @@
 #include <memory>
 #include <mutex>
 #include <optional>
-#include <ankerl/unordered_dense.h>
+#include "common/container/unordered_map.h"
 
 #include "common/common_funcs.h"
 #include "common/common_types.h"
@@ -185,7 +185,7 @@ private:
 
     mutable std::mutex mutex;
     mutable std::mutex callback_mutex;
-    ankerl::unordered_dense::map<int, ConsoleUpdateCallback> callback_list;
+    ::Common::unordered_map<int, ConsoleUpdateCallback> callback_list;
     int last_callback_key = 0;
 
     // Stores the current status of all console input

src/hid_core/frontend/emulated_controller.h

@@ -14,7 +14,7 @@
 #include <vector>
 #include <atomic>
 
-#include <ankerl/unordered_dense.h>
+#include "common/container/unordered_map.h"
 
 #include "common/common_types.h"
 #include "common/input.h"
@@ -636,7 +636,7 @@ private:
     ControllerMotionDevices virtual_motion_devices;
 
     mutable std::mutex callback_mutex;
-    ankerl::unordered_dense::map<int, ControllerUpdateCallback> callback_list;
+    ::Common::unordered_map<int, ControllerUpdateCallback> callback_list;
     int last_callback_key = 0;
 
     // Stores the current status of all controller input

src/hid_core/frontend/emulated_devices.h

@@ -10,7 +10,7 @@
 #include <functional>
 #include <memory>
 #include <mutex>
-#include <ankerl/unordered_dense.h>
+#include "common/container/unordered_map.h"
 #include <vector>
 
 #include "common/common_types.h"
@@ -205,7 +205,7 @@ private:
 
     mutable std::mutex mutex;
     mutable std::mutex callback_mutex;
-    ankerl::unordered_dense::map<int, InterfaceUpdateCallback> callback_list;
+    ::Common::unordered_map<int, InterfaceUpdateCallback> callback_list;
     int last_callback_key = 0;
 
     // Stores the current status of all external device input