feat(sink): allow upsert protobuf with text key

[xiangjinwu]

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What's changed and what's your intention?

Checklist

• I have written necessary rustdoc comments
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Documentation

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Release note

When creating a sink, format upsert encode protobuf (...) key encode text is now allowed. Note the key encode text part is required, unlike being optional for other format/encode combinations.

[tabVersion]

LGTM