Now it can handle both local vars and constants.

Currently only BinOp is implemented. More instructions will be built
later.

(for callee saved regs, we insert push/pop before reg alloc. and
after allocation, remove unnecessary ones)

we never go back to previous passes, since it is not necessary

convention(stack args), and need to optimize spill1 code

Client may pass a name with AT or PERCENTAGE, but internally MuName
does not contain that.

Ensure that "structs" have names, so that structs can be referred
symbolically. In the future, functions and basic blocks also need to be
ensured to have names. Such names are generated from their IDs if not
provided by the client.

The IR builder can create named or unnamed MuEntityHeader based on
whether it has client-provided name or not.

Can build constants now (currently only Constant::Int).

Also resolves dependency

refactor: put `aot` module and `compile_sharedlib` function under `mu::vm::testutil` module. Also updated some function calls based on updates in master branch

NOTE: Only fixed hand-written ASMs. Emitted ".s" files still have problems.