refactor(stream): add more assertion on update op handling in hash dispatcher

[BugenZhao]

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What's changed and what's your intention?

The logic for rewriting update Ops in the hash dispatcher relies on the invariant held in update_check, which is not enforced in production.

Some users encounter an assertion failure when executing this line,

risingwave/src/stream/src/executor/dispatch.rs

Line 835 in 9a01f67

StreamChunk::with_visibility(ops.clone(), chunk.columns().into(), vis_map);

where col.len() is 256 while ops.len() is 255, so I highly suspect there might be something wrong during the Op rewrite.

This PR adds some mroe assertions to help narrow down the scope of the issue.

We may also consider enabling update_check in production, or thoroughly abandon this convention as per discussion in #12539.

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• All checks passed in ./risedev check (or alias, ./risedev c)

Documentation

• My PR needs documentation updates. (Please use the Release note section below to summarize the impact on users)

Release note

If this PR includes changes that directly affect users or other significant modifications relevant to the community, kindly draft a release note to provide a concise summary of these changes. Please prioritize highlighting the impact these changes will have on users.

[stdrc]

LGTM