add possibility to choose the timezone in the UI for the datetime flow parameters

[pierreloicq]

First check

• [X] I added a descriptive title to this issue.
• [X] I used the GitHub search to find a similar request and didn't find it.
• [X] I searched the Prefect documentation for this feature.

Prefect Version

2.x

Describe the current behavior

Being in France, in my current account preference I have: Timezone: Europe/Paris

If I enter 1st March 2024 00:00 in the calendar given by the UI for datetime flow parameters, I get: "2024-03-01T00:00:00+01:00" It is something I don't want since the dataset I handle is in UTC. But it is fine that the other hours displayed in the UI (times of launch and end of the flows) are in my locale hour.

Describe the proposed behavior

So it would be nice to add the possibility to choose the timezone in the UI for the flow parameters. This is needed more than in the previous version of the UI because if I choose the date and time with the calendar and then click on the json display to correct the timezone, the date entered with the calendar disappear.

Example Use

No response

Additional context

No response