Replace externals with Conan (#3735)

* Remove git submodules that will be loaded through conan

* Move custom Find modules to their own folder

* Use conan for downloading missing external dependencies

* CI: Change the yuzu source folder user to the user that the containers run on

* Attempt to remove dirty mingw build hack

* Install conan on the msvc build

* Only set release build type when using not using multi config generator

* Re-add qt bundled to workaround an issue with conan qt not downloading prebuilt binaries

* Add workaround for submodules that use legacy CMAKE variables

* Re-add USE_BUNDLED_QT on the msvc build bot

.gitmodules

@@ -1,54 +1,30 @@
 [submodule "inih"]
     path = externals/inih/inih
     url = https://github.com/svn2github/inih
-[submodule "boost"]
-    path = externals/boost
-    url = https://github.com/yuzu-emu/ext-boost.git
-[submodule "catch"]
-    path = externals/catch
-    url = https://github.com/philsquared/Catch.git
 [submodule "cubeb"]
     path = externals/cubeb
     url = https://github.com/kinetiknz/cubeb.git
 [submodule "dynarmic"]
     path = externals/dynarmic
     url = https://github.com/MerryMage/dynarmic.git
-[submodule "fmt"]
-    path = externals/fmt
-    url = https://github.com/fmtlib/fmt.git
-[submodule "lz4"]
-    path = externals/lz4
-    url = https://github.com/lz4/lz4.git
 [submodule "unicorn"]
     path = externals/unicorn
     url = https://github.com/yuzu-emu/unicorn
-[submodule "mbedtls"]
-    path = externals/mbedtls
-    url = https://github.com/DarkLordZach/mbedtls
-[submodule "opus"]
-    path = externals/opus/opus
-    url = https://github.com/xiph/opus.git
 [submodule "soundtouch"]
     path = externals/soundtouch
     url = https://github.com/citra-emu/ext-soundtouch.git
-[submodule "libressl"]
-    path = externals/libressl
-    url = https://github.com/citra-emu/ext-libressl-portable.git
 [submodule "discord-rpc"]
     path = externals/discord-rpc
     url = https://github.com/discordapp/discord-rpc.git
 [submodule "Vulkan-Headers"]
     path = externals/Vulkan-Headers
     url = https://github.com/KhronosGroup/Vulkan-Headers.git
-[submodule "externals/zstd"]
-    path = externals/zstd
-    url = https://github.com/facebook/zstd
 [submodule "sirit"]
     path = externals/sirit
     url = https://github.com/ReinUsesLisp/sirit
+[submodule "mbedtls"]
+    path = externals/mbedtls
+    url = https://github.com/DarkLordZach/mbedtls
 [submodule "libzip"]
     path = externals/libzip/libzip
     url = https://github.com/nih-at/libzip.git
-[submodule "zlib"]
-    path = externals/zlib/zlib
-    url = https://github.com/madler/zlib.git