external: Update few submodule and remove unicorn.

- Remove all Unicorn references from language files and project as it’s deprecated and unused.
- Update SPIRV-Cross to vulkan-sdk-1.4.321.
- Update YAML to latest master.
- Fix CMake minimum version requirement errors by ensuring minimum version 3.5.

external/CMakeLists.txt

@@ -136,9 +136,6 @@ if(MSVC)
 	endif()
 endif()
 
-set(UNICORN_ARCH "arm")
-add_subdirectory(unicorn EXCLUDE_FROM_ALL)
-
 add_library(vita-toolchain INTERFACE)
 target_include_directories(vita-toolchain INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/vita-toolchain/src")