Localize edit harvest modal form

Extract hardcoded English strings in app/views/harvests/_edit_modal.html.haml
into relative i18n keys and provide translations in en, de, es, fr, ja,
and zh locale files. Add view specs for the component.

Co-authored-by: CloCkWeRX <365751+CloCkWeRX@users.noreply.github.com>
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