Rework themes to easily use light/dark palette, using only different icons

- Renamed themes:
  - "colorful" to "default" and "colorful_dark" to "default_dark"
  - "default" to "monochrome" and "default_dark" to "monochrome_dark"
  - "colorful_midnight_blue" to "qdarkstyle_midnight_blue"
  - "qdarkstyle_midnight_blue" to "qdarkstyle_midnight_blue_monochrome"
  - qdarkstyle is renamed from "Dark" to "Mine Shaft" in the UI
- default and monochrome themes all use the same qss stylesheet
- Remove the ability to select "default_dark" directly
    - Default has better support for light and dark
    - Controller and Keyboard applets icons and style adapt to dark mode
- Add "qdarkstyle_monochrome" theme
- Remove duplicated icon files

dist/qt_themes/qdarkstyle_monochrome/icons.qrc

@@ -0,0 +1,33 @@
+<!--
+SPDX-FileCopyrightText: 2018 yuzu Emulator Project & 2024 suyu Emulator Project
+SPDX-License-Identifier: GPL-2.0-or-later
+-->
+
+<RCC>
+    <!-- Theme is always dark, so we always use the same icons -->
+
+    <qresource prefix="icons/qdarkstyle_monochrome">
+        <file alias="index.theme">icons/index.theme</file>
+        <file alias="16x16/lock.png">../monochrome_dark/icons/16x16/lock.png</file>
+        <file alias="48x48/bad_folder.png">../monochrome_dark/icons/48x48/bad_folder.png</file>
+        <file alias="48x48/chip.png">../monochrome_dark/icons/48x48/chip.png</file>
+        <file alias="48x48/folder.png">../monochrome_dark/icons/48x48/folder.png</file>
+        <file alias="48x48/list-add.png">../monochrome_dark/icons/48x48/list-add.png</file>
+        <file alias="48x48/sd_card.png">../monochrome_dark/icons/48x48/sd_card.png</file>
+        <file alias="48x48/star.png">../monochrome_dark/icons/48x48/star.png</file>
+        <file alias="256x256/plus_folder.png">../monochrome_dark/icons/256x256/plus_folder.png</file>
+    </qresource>
+
+    <qresource prefix="icons/qdarkstyle_monochrome_dark">
+        <file alias="index.theme">icons/index.theme</file>
+        <file alias="16x16/lock.png">../monochrome_dark/icons/16x16/lock.png</file>
+        <file alias="48x48/bad_folder.png">../monochrome_dark/icons/48x48/bad_folder.png</file>
+        <file alias="48x48/chip.png">../monochrome_dark/icons/48x48/chip.png</file>
+        <file alias="48x48/folder.png">../monochrome_dark/icons/48x48/folder.png</file>
+        <file alias="48x48/list-add.png">../monochrome_dark/icons/48x48/list-add.png</file>
+        <file alias="48x48/no_avatar.png">../monochrome_dark/icons/48x48/no_avatar.png</file>
+        <file alias="48x48/sd_card.png">../monochrome_dark/icons/48x48/sd_card.png</file>
+        <file alias="48x48/star.png">../monochrome_dark/icons/48x48/star.png</file>
+        <file alias="256x256/plus_folder.png">../monochrome_dark/icons/256x256/plus_folder.png</file>
+    </qresource>
+</RCC>

dist/qt_themes/qdarkstyle_monochrome/icons/index.theme

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+[Icon Theme]
+Name=qdarkstyle_monochrome
+Comment=Monochrome dark theme (Mine Shaft style)
+Inherits=qdarkstyle
+Directories=16x16,48x48,256x256
+
+[16x16]
+Size=16
+
+[48x48]
+Size=48
+
+[256x256]
+Size=256

dist/qt_themes/qdarkstyle_monochrome/style.qrc

@@ -0,0 +1,8 @@
+<RCC>
+    <qresource prefix="qdarkstyle_monochrome">
+        <file alias="dark.qss">../qdarkstyle/dark.qss</file>
+    </qresource>
+    <qresource prefix="qdarkstyle_monochrome_dark">
+        <file alias="dark.qss">../qdarkstyle/dark.qss</file>
+    </qresource>
+</RCC>