feat!: Change Pandas timestamp resolution to ms for timestamp columns

[MortGron]

Description

Currently when using to_pandas on list like objects a timestamp resolution of 'ns' is enforced. In Pandas v3 the timestamp resolution is to a much larger extent inferred from the input data, where Pandas v2 would automatically set resolution 'ns'. CDF has a resolution of 'ms', so it would make sense for the to_pandas methods to also convert timestamp columns to ms.

An example where keeping resolution 'ns' would be inconenient in Pandas v3 is when using the from pandas.testing import assert_frame_equal where the resolution of timestamp columns are compared.

Another reason why chaning the resolution of columns to 'ms' would be convenient, is that a resolution of 'ms' is already set for single objects received from CDF. Only list like objects currently has a resolution of 'ns'.

Checklist:

• Tests added/updated.
• Documentation updated. Documentation is generated from docstrings - these must be updated according to your change.
  If a new method has been added it should be referenced in cognite.rst in order to generate docs based on its docstring.
• The PR title follows the Conventional Commit spec.