[flang] Rearrange some move(get<>()) calls into get<>(move()) to dodge GCC...

[flang] Rearrange some move(get<>()) calls into get<>(move()) to dodge GCC possibly-uninit warnings (bogus)

Original-commit: flang-compiler/f18@f369c6025c593f8a8b2426f2ce03c7ddec9a4ff9
Reviewed-on: https://github.com/flang-compiler/f18/pull/503
Tree-same-pre-rewrite: false