Use generated src span for catch-all case of record selector functions

This fixes #23492. The problem was that we used the real source span
of the field declaration for the generated catch-all case in the
selector function, in particular in the generated call to
`recSelError`, which meant it was included in the HIE output. Using
`generatedSrcSpan` instead means that it is not included.

(cherry picked from commit 356a2692)