[DSLX] Add a couple more (simple) precedence unit tests for the parser.
[DSLX] Add a couple more (simple) precedence unit tests for the parser.

Just wanted to put my mind at ease, unit tests are good for that. :-)

PiperOrigin-RevId: 382105658

google/xls,google/xls,google/xls,google/xls,google/xls,google/xls