Make DTA _check_compatible_with less strict by default
One of the two non-cosmetic things mentioned in #30720.

There are a bunch of places where DTA or DTI do a compatibility check that for tz_awareness_compat, but not requiring the same tz.  This check is analogous to `PeriodArray._check_compatible_with` and `TimedeltaArray._check_compatible_with`, so this adds a kwarg to _check_compatible_with so that we can use _check_compatible_with in all the relevant places and subsequently de-duplicate a bunch of code.

In addition to the comparisons, this is going to be relevant for searchsorted and insert, where we have slightly different behavior in a bunch of EA/Index subclasses.