As per the results on item 1 in T14998, declaring `catchRetry#` lazy in
its first argument opens the possibility to remove `ExnStr` complexity
from strictness demands at virtually no regressions in NoFib.

This brings `catchRetry#` in line with other primops from the `catch*`
family.

Reviewers: bgamari, simonpj, nomeata

Reviewed By: bgamari

Subscribers: thomie, carter

GHC Trac Issues: #14998, #11222

Differential Revision: https://phabricator.haskell.org/D4573