Fix adjacent slot range behavior in ASM operations

[tomerqodo]

Benchmark PR from agentic-review-benchmarks#2

[sentry]

Bug: The function parseSlotRangesOrReply no longer sends an error reply to the client on validation failure; it only frees the error string, causing silent failures.
_{Severity: HIGH}

Suggested Fix

Restore the error reporting mechanism. The line sdsfree(err); should be replaced with addReplyErrorSds(c, err); to ensure validation errors are sent to the client.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: src/cluster.c#L2015-L2016

Potential issue: In the `parseSlotRangesOrReply` function, the call to
`addReplyErrorSds(c, err)` was replaced with `sdsfree(err)`. The original
`addReplyErrorSds` function was responsible for sending the error message to the client
before freeing the memory. The new code now silently discards the validation error
without notifying the client. This affects commands like `CLUSTER MIGRATION IMPORT`,
which will fail without explanation when provided with invalid slot ranges, making
debugging difficult for operators.

_{Did we get this right? 👍 / 👎 to inform future reviews.}

[sentry]

Bug: The comparison function slotRangeArrayIsEqual now mutates its input arrays by merging slot ranges, which is an unexpected and potentially breaking side effect.
_{Severity: MEDIUM}

Suggested Fix

The slotRangeArrayIsEqual function should not modify its inputs. It should either perform the comparison on copies of the arrays or use a non-mutating comparison logic to check for equality.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: src/cluster.c#L1879-L1880

Potential issue: The comparison function `slotRangeArrayIsEqual` now has a side effect
of modifying its input arrays. It calls `slotRangeArraySortAndMerge`, which sorts and
merges slot ranges, altering the `num_ranges` field and the contents of the arrays. This
violates the principle that comparison functions should not mutate their inputs. Callers
that reuse an array after passing it to `slotRangeArrayIsEqual` may operate on
unexpectedly modified data, leading to subtle bugs.

_{Did we get this right? 👍 / 👎 to inform future reviews.}