Literal inlay hints should appear when the type isn't obvious

[DetachHead]

a = "asdf"  # no inlay because the type is obviously Literal["asdf"]

for c in ("bar",):
    b = c  # no inlay, but it should because the type is not obvious

• original issue: statically determine how many times a non-variadic tuple (and/or Iterable) will be iterated over #348
• related: inlay hints appear on Literal types when there's more than one value in the Literal #174