### What changes were proposed in this pull request?
In the PR, I propose to override the `sql` and `toString` methods of the expressions that implement operators over ANSI intervals (`YearMonthIntervalType`/`DayTimeIntervalType`), and replace internal expression class names by operators like `*`, `/` and `-`.
### Why are the changes needed?
Proposed methods should make the textual representation of such operators more readable, and potentially parsable by Spark SQL parser.
### Does this PR introduce _any_ user-facing change?
Yes. This can influence on column names.
### How was this patch tested?
By running existing test suites for interval and datetime expressions, and re-generating the `*.sql` tests:
```
$ build/sbt "sql/testOnly *SQLQueryTestSuite -- -z interval.sql"
$ build/sbt "sql/testOnly *SQLQueryTestSuite -- -z datetime.sql"
```
Closes#32262 from MaxGekk/interval-operator-sql.
Authored-by: Max Gekk <max.gekk@gmail.com>
Signed-off-by: Max Gekk <max.gekk@gmail.com>
e8d6992b66