[11.x] php 8.3 follow up for enum in Datetime range formatter

Confused about what exactly was the problem. #2827055-141: Add option to show only start or end date in the DateTime Range custom formatter → points to https://stitcher.io/blog/new-in-php-82#fetch-properties-of-enums-in-cons... but that is about fetching enum properties in const expressions, which I couldn't find any instances of in the revert commit.

Regardless, I think this issue needs more information about what we're trying to do here. Something like "Convert DateTimeRangeConstants interface to DateTimeRangeDisplayOptions enum".

Guess it's also postponed until ✨ Add option to show only start or end date in the DateTime Range custom formatter Needs review is back in.

Tried to clarify the task a little.

✨ Add option to show only start or end date in the DateTime Range custom formatter Needs review is in.

I think we need to deprecate the consts and keep them around. Also seems we are likely to move to UpperCamelCase for enums as per #3339746: Decide on a coding style for PHP Enumerations → .

Thanks for pointing that out, @mstrelan.
I added back the interface and marked it for removal in 11.1, but this is of course to be discussed.
Change the enum cases to UpperCamelCase.

Guess we now need a follow up for the removal, and also a change record.

Left a comment on the MR.

Why are the cases coded in camel case? They are like constants. Shouldn't we use uppercase for them?

@chi see #9 and the issue linked there for discussion on casing

Rebased the MR and created a CR draft.
Also updated the deprecation target to 11.2.0 and the removal target to 12.0.0.
Please review.

Not sure if we need a followup for the removal of the deprecated interface.