Add WriteBatch::Handler::LogData iteration callback function

[hemal-shah]

Change adds log_data_ function callback for when iterating over a WriteBatch. Previously only the Put, Delete, Merge operations were called into when iterating over an WriteBatch (and their *_cf equivalent through a different WriteBatch::Handler implementation).

To maintain backwards compatibility, previously exported function definitions remain the same, but new functions are exported for different languages to use the LogData callback on an iteration.

Background

Hi - we use the rust-rocksdb bindings to work with rocksdb at Stripe. We are starting to make small contributions #14183 & #14136 and this adds on top of it. I saw that the PutLogData method is already exported for a WriteBatch, but there's no way to consume that. This change allows us to consume that information (with a follow up change on the rust-rocksdb repo.).

Thanks for your time looking into this. Previously we had trouble with meta's internal linters - I am happy to make appropriate change if something like that pops up again.

Note

FYI - I am on a vacation for the next week, so I wouldn't be able to make follow-up changes until 01/26/2026 (hopefully the PR wouldn't close automatically by then).

[meta-cla]

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[hemal-shah]

Signed CLA. Probably will take 1 hour to reflect on the failing check as per documentation.

[meta-cla]

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