[SPARK-20963][SQL][FOLLOW-UP] Use UnresolvedSubqueryColumnAliases for visitTableName

[maropu]

What changes were proposed in this pull request?

This pr (follow-up of #18772) used UnresolvedSubqueryColumnAliases for visitTableName in AstBuilder, which is a new unresolved LogicalPlan implemented in #18185.

How was this patch tested?

Existing tests

[SparkQA]

Test build #80294 has finished for PR 18857 at commit 93d5b24.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
• case class UnresolvedRelation(tableIdentifier: TableIdentifier)

[maropu]

@gatorsmile ok.

[gatorsmile]

LGTM

Thanks! Merging to master.