[cmake] refactor: cpmfile, deps prefetch, force system and more (#322)

CPM Dependencies are now managed in a singular json file, where each can be properly prefetched at-will via `tools/cpm-fetch.sh <packages...>`, or all at once via `tools/cpm-fetch-all.sh`.

Adds docs for CPMUtil as well.

Also adds `<package>_FORCE_{BUNDLED,SYSTEM}` overrides

Signed-off-by: crueter <[email protected]>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/322
Reviewed-by: CamilleLaVey <[email protected]>

.gitignore

@@ -52,3 +52,4 @@ Thumbs.db
 eden-windows-msvc
 artifacts
 *.AppImage*
+/install*