BUGFIX: Use 12/24 hour format for DateTimePicker depending on configured format

[Alvadda]

Currently the DateTimePicker always uses the 12h time format even if the time format specified is in 24h format.

Currently supported hour formats from docs:

g: hour without leading zeros - 12-hour format - 1 through 12
G: hour without leading zeros - 24-hour format - 0 through 23
h: 12-hour format of an hour with leading zeros - 01 through 12
H: 24-hour format of an hour with leading zeros - 00 through 23

This change ensures that the 24h format is used for entering times when a 24h format was configured.

For testing:

dateTime24h:
  type: DateTime
    inspector:
      editorOptions:
        format: d-m-Y H:i
dateTime12h:
  type: DateTime
    inspector:
      editorOptions:
        format: d-m-Y h:i a

Fixes partly : #3412

[grebaldi]

Hi @Alvadda,

nice work! Deriving this from the configured format makes complete sense and I was able to test your change locally to verify that it works like a charm 👍

Just one minor nitpick on the code, that's all :)

Since this is being treated as BUGFIX, the PR should target 8.3 rather than 8.4.

[grebaldi]

Thanks for the adjustments, @Alvadda 👍