* Split plural strings with multiple sentences to avoid duplicating translations.
* Decouple strings where the singular and plural form are not just the same string with different numbers, but essentially two different strings.
* Use an established pattern for numbered placeholders in translator comments.
* Replace constants in translatable strings with placeholders, mark them as code.
* Make sure sentences are translated as a whole, not as separate string parts.
* Remove unnecessary context and escaping.
Props ocean90, SergeyBiryukov.
See #46683.
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