sTest: add toThrow, allow multiple expect clauses in one test

[OAGr]

Description of suggestion or shortcoming:

Claude and such keep on trying to do this:

@name("Test Cost Calculation Function")
testCostCalculationFn = sTest.test(
  "costCalculationFn handles invalid inputs",
  {
    ||
    sTest.expect(costCalculationFn(0, 35000, 3.5, 100, 5)).toThrow()
    sTest.expect(costCalculationFn(20000, 35000, -1, 100, 5)).toThrow()
  }
)

Note that it both has toThrow() and the rest of it.

Requires: #3395