Math operators for should fail on String

[piotrszul]

Only + operator should be supported for Strings.

(Math 6 exlusions)

Details

Expected error but got value: one (au.csiro.pathling.fhirpath.collection.StringCollection@10471faa)

• s5 * s5 [** Error multiplying string (3)]

(FHIR R4 exlusions)

Details

Expected error but got value: false (au.csiro.pathling.fhirpath.collection.BooleanCollection@3af8fe89)

• 'a'-'b' = 'ab' [** testMinus4]

[piotrszul]

'+' will be implemented a new feature in #2154. Here resolution to make all arithmetic operator unsupported for String.