Add ABC instructions get_desc_arity_offset, get_thunk_desc and...

Add ABC instructions get_desc_arity_offset, get_thunk_desc and load_module_name (recently added for GraphCopy).

See the relevant commits to the code generator:

• https://gitlab.science.ru.nl/clean-compiler-and-rts/code-generator/commit/067dc605f008f1180587509a0b56b20d478d2ed7
• https://gitlab.science.ru.nl/clean-compiler-and-rts/code-generator/commit/f69e478f131fbc21a2418a758a42cd20f87a000f
• https://gitlab.science.ru.nl/clean-compiler-and-rts/code-generator/commit/c6ea6110e9639465f3dece868ebce9747c52e35f