[DocDB] Enhance protection against incorrect DocDB records

[ttyusupov]

Jira Link: DB-11191

Description

In #22057 we've faced an issue with having incorrect records like <row> -> null inside regular DB that are processed in an unexpected way by read iterator and results in rows either absent or having null non-PK values depending on whether select statement is aggregate or not and whether it has where clause.

We should have a protection against incorrect records and throw an error rather than having an undefined behaviour resulting in returning incorrect data.

Issue Type

kind/bug

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