[Fix] Disable updating pk value

[kTrzcinskii]

No description provided.

[Copilot]

Pull request overview

This PR disables updating primary key column values by adding validation in both the analyzer and executor layers to reject UPDATE statements that attempt to modify primary key columns.

Changes:

• Added PrimaryKeyCannotBeUpdated error variant to the analyzer
• Implemented primary key update validation in the analyzer's analyze_update_statement method
• Added redundant runtime validation in the executor's update handler (with associated performance and maintainability concerns)
• Added comprehensive test coverage for both single and multiple column update scenarios

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
planner/src/analyzer.rs	Added new error type and validation logic to prevent primary key updates during analysis phase; includes unit tests
executor/src/statement_executor.rs	Added redundant runtime validation check for primary key updates in the executor
executor/src/lib.rs	Added integration tests to verify primary key update prevention works end-to-end

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