Remove pendulum from schedules (dagster-io#21391)

Noticed that `pendulum` was using up alot of CPU time. This PR uses native `datetime` instead to improve performance inside of schedules, the result is then converted to a `pendulum.datetime` at the end before yielding. 

This slightly improves performance ~10% or so. The next step would be to replace all the rest of the pendulum callsites outside of schedules and stop returning `pendulum.datetime` from our definitions. This would net a large performance improvement around 4x the current status quo.

I also fixed a very small bug where schedules didn't account for non-hour DST transitions.

### Test plan

running buildkite test coverage

python_modules/dagster/dagster/_seven/compat/datetime.py

@@ -0,0 +1,12 @@
+# pyright: reportMissingImports=none
+try:
+ # zoneinfo is python >= 3.9
+ from zoneinfo import ZoneInfo as _timezone_from_string
+except:
+ from dateutil.tz import gettz as _timezone_from_string
+from datetime import tzinfo
+from typing import Optional
+
+
+def timezone_from_string(timezone_name: str) -> Optional[tzinfo]:
+ return _timezone_from_string(timezone_name)

python_modules/dagster/dagster/_seven/compat/pendulum.py

@@ -45,7 +45,12 @@ def mock_pendulum_timezone(override_timezone):
 
 def create_pendulum_time(year, month, day, *args, **kwargs):
  if "tz" in kwargs and "dst_rule" in kwargs and _IS_PENDULUM_1:
- tz = pendulum.timezone(kwargs.pop("tz"))
+ tz_name_or_info = kwargs.pop("tz")
+ tz = (
+ pendulum.timezone(tz_name_or_info)
+ if isinstance(tz_name_or_info, str)
+ else tz_name_or_info
+ )
  dst_rule = kwargs.pop("dst_rule")
 
  return pendulum.instance(