Fix update_all to correctly handle Arel nodes

[rscq]

Summary

Fix update_all to correctly handle updates containing Arel nodes.

Background

The current update_all implementation serializes update values using sanitize_sql_for_assignment.
However, this method cannot convert Arel nodes (e.g., Arel::Nodes::Addition) to SQL, causing runtime errors in the following cases:

• increment! / decrement! (internally generates Arel expressions like column + 1)
• counter_culture gem (uses Arel expressions for counter updates)

This issue has also been reported in the upstream repository (citusdata#282).

Changes

Aligned with Rails' own update_all implementation by using _substitute_values for Hash updates.

• Hash updates: Uses _substitute_values to preserve Arel nodes as-is and convert other values to bind parameters
• String updates: Processed with sanitize_sql_for_assignment as before
• Optimistic Locking: Reproduces the same lock_version auto-increment behavior as Rails

Reference: Rails implementation

https://github.com/rails/rails/blob/8-1-stable/activerecord/lib/active_record/relation.rb#L615-L625

Note

Due to the use of _substitute_values, the generated SQL now uses bind parameters ($1, $2...) instead of literal values.
Existing SQL string comparison tests have been adjusted accordingly.

[a5-stable]

Thanks for your contribution! It looks good to me.
The failing test doesn’t seem related to this PR. It should be resolved in #23