Support timezone-aware datetime objects

[butson]

connection:

• Added support for explicit TimeZone connection property

datatype:

• Use Julian calendar for date/datetime before 1582 Oct 4. When the Gregorian calendar was introduced: . The day after October 4, 1582 (Julian) became October 15, 1582 (Gregorian). . That 10-day jump is not accounted for in C's calendar logic. . Julian calendar handles leap years differently. The utc calendar the engine is using understands this the python functions based on C calendar logic do not.
• time.mktime , time.localtime don't support older dates while engine does changing to use calendar above and calculate time, avoid these issues.
• use of datetime + timezone should handle daylight savings times and not be off by an hour.

tests:

• Use connection property TimeZone to change timezone
• Support timezone-aware datetime
• Use pytz correctly with localize if pytz is used
• Use zoneinfo.ZoneInfo if available

encodedsession:

• Manage and verify TimeZone settings on per connection basis
• Allows connections with different TimeZone setting from same application

requirements.txt:

• Add requirement for tzlocal, should be available on all supported python versions. There is a change in api between releases , this is handled in the code.

[butson]

I expect the cursor test failure is related to the callback to engine to get the real time zone used.