[tools, cmake] refactor: update/hash check scripts, use tags for some more deps, proper CPMUtil separation (#2666)

Uses tags for a bunch of deps that can use them

Also adds a bunmch of scripts to tools/cpm, notably for checking hashes
and checking for updates.

TODO for the future:
- CI target to check hashes
- Weekly CI to check for updates

Need to get that other CI runner up

additional stuff

- Ports gentoo fixes
- makes solaris work (TODO: sdl2)
- way better docs
- properly separates CPMUtil as a standalone project

Reviewed-on: #2666
Reviewed-by: Lizzie <lizzie@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

docs/CPMUtil.md

@@ -0,0 +1,14 @@
+# CPMUtil
+
+CPMUtil is a wrapper around CPM that aims to reduce boilerplate and add useful utility functions to make dependency management a piece of cake.
+
+See more in [its repository](https://git.crueter.xyz/CMake/CPMUtil)
+
+Eden-specific options:
+
+- `YUZU_USE_CPM` is set by default on MSVC and Android. Other platforms should use this if certain "required" system dependencies (e.g. OpenSSL) are broken or missing
+  * If this is `OFF`, required system dependencies will be searched via `find_package`, although most externals use CPM regardless.
+
+## Tooling
+
+See the [tooling docs](../tools/cpm)