[SPARK-21472][SQL][FOLLOW-UP] Introduce ArrowColumnVector as a reader for Arrow vectors.

[ueshin]

What changes were proposed in this pull request?

This is a follow-up of #18680.

In some environment, a compile error happens saying:

.../sql/core/src/main/java/org/apache/spark/sql/execution/vectorized/ArrowColumnVector.java:243:
error: not found: type Array
  public void loadBytes(Array array) {
                        ^

This pr fixes it.

How was this patch tested?

Existing tests.

[viirya]

LGTM

[SparkQA]

Test build #79831 has finished for PR 18701 at commit 55766b5.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[cloud-fan]

LGTM, merging to master!