Drop generated timelib lexer files

[mvorisek]

based on #21206 (comment)

The ext/date/lib/parse_date.c and ext/date/lib/parse_iso_intervals.c files are generated from their .re files.

The C files are newly generated like other lexer files for json, phar... This unifies the build process and simplifies upstream updates, patches...

[iluuu1994]

Can a RM (e.g. @edorian or @DanielEScherzer) confirm whether this needs changes in the release process? I think there are some manual steps involved for generating the language parser files. Maybe this would need to be added to some docs.

[DanielEScherzer]

Can a RM (e.g. @edorian or @DanielEScherzer) confirm whether this needs changes in the release process? I think there are some manual steps involved for generating the language parser files. Maybe this would need to be added to some docs.

I think this would need a change, but not tested yet

But what if instead, we just kept the generated files in this repo, and updated the github tests that make sure generated files are up to date to include these files too?

[iluuu1994]

The output of re2c is bound to change in the future, so I personally think it's better to do this as a build step, especially given re2c is already a dependency for builds from source (from GH at least).