Enable "organize imports on save"

I would like to enable organize imports on save and would like to get feedback from jdt.core commiters.

Known benefit: i don't have to manually remove no longer used imports.
Known downslde: The first commit on each file will have a longer - unrelated - patch size.

optional workaround: reorganize all imports once for all files.
history: at some point of time the sort order for imports was changed.

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If you start a discussion and mention me, I will add more details there. Hint: if the change of strategy is done well, I'm not strictly against it.

_Originally posted by @stephan-herrmann in https://github.com/eclipse-jdt/eclipse.jdt.core/pull/1700#discussion_r1641778187_