DateInput: fix `Cmd+S` in nested structures

[distantnative]

Description

Summary of changes

• DateInput.vue does not use anymore the global keydown.cmd.s event to commit unfinished input, but rather listens to the event locally, preventing propagation and only emits a submit event once the input value has been committed/transofrmed to a proper date time object and emitted/updated.

Reasoning

• Using the global keydown.cmd.s event has been triggering the onBlur() method no matter whether the date input was actually being edited or just present in the current view. We only need to trigger it when the input is currently being edited (as @blur will take care of committing the value when the focus changes away from the input already).
• To avoid the previous race conditions, we listen locally for the event (prevent default and stop propagation), commit then the value to a real datetime object and emit the submit event. We do not use this.$events.emit("keydown.cmd.s") as this triggers a race condition, where the input event is still propagating up the chain when the save would also happen. Emitting submit ensures that this event has to travel up the same chain as the input event and thus they arrive in the right order.

Changelog

Fixes

• Using Cmd + S/Ctrl + S in nested structures/objects with date fields does not corrupt data anymore

  6390

Ready?

• [x] In-code documentation (wherever needed)
• [x] Tests and CI checks all pass

For review team

• [x] Add changes & docs to release notes draft in Notion

[bezin]

Fantastic, thanks for this fix, much appreciated! Shouldn't this be target at 4.3.1, though?

[distantnative]

@bezin I only like to include fixes that are very simple in patch releases. When we're super sure of no regressions. As they don't get any release candidate.

I'm not that 100% sure with this one. So I rather want to include it in 4.4