Connector Builder UI: Allow configuring cursor_datetime_format

[lmossman]

Context

The FE side of #28782

This should look like a combobox that suggests common datetime formats, but it should allow multiple values to be entered, so we will need to modify our ComboBox component to support multiple values.

Whatever value the user puts there should be set as the cursor_datetime_format value in the converted manifest.

Acceptance Criteria

• Users can configure cursor_datetime_format array in the Builder UI
• Common datetime formats are still suggested

[lmossman]

• Don't support multiple values for now
• Add an outgoing datetime format input to the Advanced section, make it optional, and if it is unset, just use the cursor datetime format as the outgoing datetime format in the manifest