fix: ArrayIter does not report size hint correctly after advancing from the iterator back (#8728)

# Which issue does this PR close?

N/A

# Rationale for this change

for the fix: the array iterator is marked as exact size iterator and
double ended iterator so it should report the current length when
accessed through the other side

# What changes are included in this PR?

fix by using `current_end` instead of `array.len()`
and also adds a LOT of tests extracted from (which is how I found that
bug):
- #8697

# Are these changes tested?

Yes

# Are there any user-facing changes?

Kinda

Author: rluvaton