[flang][codegen] ensure descriptor lower bounds are LBOUND compliant

Follow-up of https://reviews.llvm.org/D121488 to ensure all descriptors
created inline complies with LBOUND requirement that the lower bound is
`1` when the related dimension extent is zero.

Both fir.xrebox and fir.xembox codegen is updated to enforce this
constraint.

Also upstream the "normalized lower bound" attribute that was added in fir-dev
since embox codegen was upstreamed, it is conflicting with this patch
otherwise.

Differential Revision: https://reviews.llvm.org/D122419