core: Remove usage of unicorn

Unicorn long-since lost most of its use, due to dynarmic gaining support
for handling most instructions. At this point any further issues
encountered should be used to make dynarmic better.

This also allows us to remove our dependency on Python.

.gitmodules

@@ -7,9 +7,6 @@
 [submodule "dynarmic"]
     path = externals/dynarmic
     url = https://github.com/MerryMage/dynarmic.git
-[submodule "unicorn"]
-    path = externals/unicorn
-    url = https://github.com/yuzu-emu/unicorn
 [submodule "soundtouch"]
     path = externals/soundtouch
     url = https://github.com/citra-emu/ext-soundtouch.git