Allow passing timezone to List Schedules API

[NasAmin]

Hi,

The list schedule API currently does not allow passing in a timezone. As a result it returns dates in the accounts default timezone. We are trying to list all schedules and then generate terraform from it however, the dates come out wrong because the schedule timezone is different than the default account timezone.

We can convert the timezone but it would be easier if default for list schedules was UTC. At least allowing to pass the timezone should help with this.