[flang] Run expression semantic analysis with rest of semantics.

checkpoint array constructor semantics work

checkpoint

array constructors of lengthless intrinsic types

checkpoint

Correct ambiguous substring refs misparsed as array elements

Original-commit: flang-compiler/f18@2232549efe42a2ef97725a131ac642b9be9274f4
Reviewed-on: https://github.com/flang-compiler/f18/pull/271
Tree-same-pre-rewrite: false