[SPARK-20013][SQL]merge renameTable to alterTable in ExternalCatalog

[windpiger]

What changes were proposed in this pull request?

merge renameTable to alterTable in ExternalCatalog has some reasons:

In Hive, we rename a Table by alterTable
Currently when we create / rename a managed table, we should get the defaultTablePath for them in ExternalCatalog, then we have two defaultTablePath logic in its two subclass HiveExternalCatalog and InMemoryCatalog, additionally there is also a defaultTablePath in SessionCatalog, so till now we have three defaultTablePath in three classes.
we'd better to unify them up to SessionCatalog
To unify them, we should move some logic from ExternalCatalog to SessionCatalog, renameTable is one of this.

while limit to the simple parameters in renameTable

  def renameTable(db: String, oldName: String, newName: String): Unit

even if we move the defaultTablePath logic to SessionCatalog, we can not pass it to renameTable.

So we can merge the renameTable to alterTable, and rename it in alterTable.

How was this patch tested?

delete some tests in ExternalCatalogSuite which already existed in SessionCatalogSuite,
and move some other tests in ExternalCatalogSuite which does not exist in SessionCatalogSuite

[SparkQA]

Test build #76038 has finished for PR 17721 at commit 2ea645c.

• This patch fails Scala style tests.
• This patch does not merge cleanly.
• This patch adds no public classes.

[hvanhovell]

@windpiger could you make sure that the freshly added events still work after this change.

[HyukjinKwon]

ping @windpiger

[gatorsmile]

We are closing it due to inactivity. please do reopen if you want to push it forward. Thanks!