BUG: Resample across multiple days

Fixes an issue where resampling over multiple days causes a ValueError
when a number of days between the normalized first and normalized last
days is not a multiple of the frequency.

Added test TestResample.test_resample_anchored_multiday

Closes #8683
Merge pull request #8941 from hkleynhans/fix/8683_resample_value_error

BUG: Resample across multiple days