### What changes were proposed in this pull request?
Verify ALTER TABLE CHANGE COLUMN with Char and Varchar and avoid unexpected change
For v1 table, changing type is not allowed, we fix a regression that uses the replaced string instead of the original char/varchar type when altering char/varchar columns
For v2 table,
char/varchar to string,
char(x) to char(x),
char(x)/varchar(x) to varchar(y) if x <=y are valid cases,
other changes are invalid
### Why are the changes needed?
Verify ALTER TABLE CHANGE COLUMN with Char and Varchar and avoid unexpected change
### Does this PR introduce _any_ user-facing change?
no
### How was this patch tested?
new test
Closes#30833 from yaooqinn/SPARK-33834.
Authored-by: Kent Yao <yaooqinn@hotmail.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
f5fd10b1bc