Stop converting timestamp to dt.datetime (leave as bintime)

[mjohanse-emr]

Tech Debt

For now, I am having to convert a bintime.DateTime to datetime.datetime to get around a mypy error with the named Timing constructor methods.

C:\dev\nipanel-python>poetry run mypy
src\nipanel\converters\protobuf_types.py:121: error: Argument "timestamp" to "Timing" has incompatible type "DateTime"; expected "datetime | None"  [arg-type]
Found 1 error in 1 file (checked 28 source files)

See this PR comment thread:
#75 (comment)

AB#3168483

[mjohanse-emr]

This issue was resolved as part of #75