[C++][Gandiva] Add token and grammar rules for if and bool

**Reporter**: [Jin Shang](https://issues.apache.org/jira/browse/ARROW-17744) / @js8544

_{**Note**: *This issue was originally created as [ARROW-17744](https://issues.apache.org/jira/browse/ARROW-17744). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start by locating Gandiva's tokenizer and grammar entry points; the payload does not name specific files or tests. Add the token and grammar rules for `if` and `bool`, then verify that Gandiva accepts those constructs according to the issue requirements.

Written by the indexing model from the issue text.