[cmake, tools] update CPMUtil and add support for CPMUtil bundled Qt, module updates, cleanups (#3289)

Support for bundled Qt, not through aqtinstall but rather my CI. Multimedia is
implemented too, works on both Windows and Linux, though we don't
actually use it so it doesn't really matter. Contains Declarative and all that so the Quick frontend will work once it becomes a thing.

Some options have changed, notably w.r.t LTO and faster
linker, which are now handled directly in the modules.

CPMUtil also has support for custom dirs (`PackageName_CUSTOM_DIR`) now. Probably most useful for adding external fragment shaders and whatnot.

Signed-off-by: crueter <crueter@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3289

externals/cmake-modules/GetSCMRev.cmake

@@ -1,5 +1,5 @@
 # SPDX-FileCopyrightText: Copyright 2025 crueter
-# SPDX-License-Identifier: GPL-3.0-or-later
+# SPDX-License-Identifier: LGPL-3.0-or-later
 
 ## GetSCMRev ##
 # Name is self explanatory. Gets revision information from files, OR from git.
@@ -13,6 +13,8 @@ find_package(Git QUIET)
 # tag:    git describe --tags --abbrev=0
 # branch: git rev-parse --abbrev-ref=HEAD
 
+# TODO: string overrides
+
 function(run_git_command variable)
     if(NOT GIT_FOUND)
         set(${variable} "GIT-NOTFOUND" PARENT_SCOPE)