[flang] Optimize redundant array repacking. (#147881)
This patch allows optimizing redundant array repacking, when
the source array is statically known to be contiguous.
This is part of the implementation plan for the array repacking
feature, though, it does not affect any real life use case
as long as FIR inlining is not a thing. I experimented with
simple cases of FIR inling using `-inline-all`, and I recorded
these cases in optimize-array-repacking.fir tests.
