Allow creating of TimeUnit instances without direct dependency on parquet-format

[pacman82]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

Maintaimer of the downstream odbc2parquet tool here. I would like to switch from converted type to logical types. One bump in the road of doing so is the fact that odbc2parquet now directly needs to depend also on the parquet-format crate instead of just parquet. The cause being, that it is impossible to create an instance of TimeUnit for the logical type, due to it being depended on e.g. MilliSeconds or MicroSeconds type of the parquet-format crate.

Describe the solution you'd like

I think I do not fully grasp why the current design has been choosen, so I am not particularly biased towards any solution. I could brainstorm a few ideas though:

• Drop the MilliSeconds type tag from the TimeUnit::MILLIS variant.
• Give TimeUnit constructors for milliseconds, microseconds, etc.
• Reexport MilliSeconds, MicroSeconds, etc. ..

Describe alternatives you've considered

Currently I'll just add the extra direct dependency to parquet-format. If this is what you want me to do, consider this issue void.
Additional context

[alamb]

👋 I believe #2626 from @tustvold has removed the dependency entirely on parquet-format (by inlining the definitions) so hopefully you won't need any direct dependencies after the next release (tracked by #2665 )

[pacman82]

@alamb Thanks for the information and quick response.
@tustvold Thanks for inlining.

Cheers, Markus

[alamb]

I believe this is now resolved

[pacman82]

I believe this is now resolved

Yes it is. Already in use downstream. Thanks!