[flang] improve and rename Entity::hasNonDefaultLowerBounds (#93848)

Improve hasNonDefaultLowerBounds to follow box fir.convert. This helps
HLFIR helpers to generate less code when it can be easily deduced that
the fir.box lower bounds were set to ones.

It will help me for SELECT RANK lowering to avoid generating
hlfir.declare with lower bounds inside the RANK CASE (Current situation
would not be incorrect, the lower bounds would be SSA value ending-up
being one, I just want simpler IR).

Renamed to mayHaveNonDefaultLowerBounds since it may still answer yes when
the lower bounds are ones.