[SPARK-5278][SQL] Introduce UnresolvedGetField and complete the check of...

[SPARK-5278][SQL] Introduce UnresolvedGetField and complete the check of ambiguous reference to fields

When the `GetField` chain(`a.b.c.d.....`) is interrupted by `GetItem` like `a.b[0].c.d....`, then the check of ambiguous reference to fields is broken.
The reason is that: for something like `a.b[0].c.d`, we first parse it to `GetField(GetField(GetItem(Unresolved("a.b"), 0), "c"), "d")`. Then in `LogicalPlan#resolve`, we resolve `"a.b"` and build a `GetField` chain from bottom(the relation). But for the 2 outer `GetFiled`, we have to resolve them in `Analyzer` or do it in `GetField` lazily, check data type of child, search needed field, etc. which is similar to what we have done in `LogicalPlan#resolve`.
So in this PR, the fix is just copy the same logic in `LogicalPlan#resolve` to `Analyzer`, which is simple and quick, but I do suggest introduce `UnresolvedGetFiled` like I explained in https://github.com/apache/spark/pull/2405.

Author: Wenchen Fan <cloud0fan@outlook.com>

Closes #4068 from cloud-fan/simple and squashes the following commits:

a6857b5 [Wenchen Fan] fix import order
8411c40 [Wenchen Fan] use UnresolvedGetField