Spark 4.2: ANSI arithmetic overflow tests fail under Comet

[andygrove]

Several Comet arithmetic tests are skipped on Spark 4.2 (assume(!isSpark42Plus, ...)) pending investigation of ANSI overflow behavior differences introduced in Spark 4.2.

Affected tests in CometExpressionSuite:

• "unary negative integer overflow test"
• "ANSI support for add"
• "ANSI support for subtract"
• "ANSI support for multiply"

These were bulk-deferred to the generic Spark 4.2 tracker in #4126. This issue tracks the specific ANSI arithmetic overflow work so the assume guards can be removed.