### What changes were proposed in this pull request?
This PR proposes to improve the exception messages while `UnresolvedTable` is handled based on this suggestion: https://github.com/apache/spark/pull/30321#discussion_r521127001.
Currently, when an identifier is resolved to a view when a table is expected, the following exception message is displayed (e.g., for `COMMENT ON TABLE`):
```
v is a temp view not table.
```
After this PR, the message will be:
```
v is a temp view. 'COMMENT ON TABLE' expects a table.
```
Also, if an identifier is not resolved, the following exception message is currently used:
```
Table not found: t
```
After this PR, the message will be:
```
Table not found for 'COMMENT ON TABLE': t
```
### Why are the changes needed?
To improve the exception message.
### Does this PR introduce _any_ user-facing change?
Yes, the exception message will be changed as described above.
### How was this patch tested?
Updated existing tests.
Closes#30461 from imback82/unresolved_table_message.
Authored-by: Terry Kim <yuminkim@gmail.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
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