Fix nested calls

[StrongerXi]

Existing translation from nested calls in Lir to X86 temp instructions might result in clobbering of temps that hold result of previous arguments, e.g.,

Call(42, Call(0, ...))
--->
Targ0 = 42
... translate Call(0, ...), which involves [Targ0 = 0]...
Call Targ0

The bug didn't show up in existing simple integration tests because

• Primitive functions have no freevar, so the closure argument can be safely clobbered
• To clobber the second argument, we need a call expression in the third argument, but 1 + 2 + 3 is left-associative, so no good.

The enhanced integration in this PR test is probably the bare-minimum regression test for this bug.