refactor: convert to mysql values directly from arrow

[MichaelScofield]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

What's changed and what's your intention?

so that there are no intermediate Values to occupy memory, and the performance for iterating record batch is significantly better:

from iter_record_batch_rows.rs:

iter_record_batch/by_greptimedb_values/1
                        time:   [194.58 ns 198.29 ns 201.68 ns]
iter_record_batch/by_loop_rows_and_columns/1
                        time:   [22.715 ns 22.834 ns 22.965 ns]
iter_record_batch/by_datafusion_scalar_values/1
                        time:   [74.872 ns 75.163 ns 75.510 ns]
iter_record_batch/by_datafusion_scalar_values_with_buf/1
                        time:   [77.063 ns 77.415 ns 77.786 ns]
iter_record_batch/by_greptimedb_values/10
                        time:   [391.12 ns 393.26 ns 395.50 ns]
iter_record_batch/by_loop_rows_and_columns/10
                        time:   [95.108 ns 96.171 ns 97.482 ns]
iter_record_batch/by_datafusion_scalar_values/10
                        time:   [602.60 ns 605.13 ns 607.61 ns]
iter_record_batch/by_datafusion_scalar_values_with_buf/10
                        time:   [381.24 ns 382.93 ns 384.55 ns]
iter_record_batch/by_greptimedb_values/100
                        time:   [2.8510 µs 2.8677 µs 2.8859 µs]
iter_record_batch/by_loop_rows_and_columns/100
                        time:   [748.73 ns 750.04 ns 751.43 ns]
iter_record_batch/by_datafusion_scalar_values/100
                        time:   [6.0008 µs 6.0182 µs 6.0378 µs]
iter_record_batch/by_datafusion_scalar_values_with_buf/100
                        time:   [3.4424 µs 3.4534 µs 3.4646 µs]
iter_record_batch/by_greptimedb_values/1000
                        time:   [27.471 µs 27.617 µs 27.767 µs]
iter_record_batch/by_loop_rows_and_columns/1000
                        time:   [7.3151 µs 7.3463 µs 7.3815 µs]
iter_record_batch/by_datafusion_scalar_values/1000
                        time:   [58.915 µs 59.231 µs 59.632 µs]
iter_record_batch/by_datafusion_scalar_values_with_buf/1000
                        time:   [33.747 µs 33.856 µs 33.972 µs]
iter_record_batch/by_greptimedb_values/10000
                        time:   [270.98 µs 272.14 µs 273.35 µs]
iter_record_batch/by_loop_rows_and_columns/10000
                        time:   [72.313 µs 72.386 µs 72.475 µs]
iter_record_batch/by_datafusion_scalar_values/10000
                        time:   [589.19 µs 591.01 µs 592.89 µs]
iter_record_batch/by_datafusion_scalar_values_with_buf/10000
                        time:   [335.18 µs 336.08 µs 337.07 µs]

PR Checklist

Please convert it to a draft if some of the following conditions are not met.

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.
• API changes are backward compatible.
• Schema or data changes are backward compatible.

[Copilot]

Pull Request Overview

This PR refactors the MySQL writer to convert Arrow arrays directly to MySQL values instead of using intermediate GreptimeDB Value objects, resulting in significant performance improvements for iterating record batches.

Key changes:

• Replaced Value-based iteration with direct Arrow array processing in the MySQL writer
• Added benchmark tests to demonstrate performance improvements
• Updated dependencies to support new direct conversion approach

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 8 comments.

File	Description
src/servers/src/mysql/writer.rs	Complete refactor of record batch processing to use direct Arrow array access instead of Value objects
src/servers/Cargo.toml	Added common-decimal dependency for direct decimal handling
src/common/recordbatch/benches/iter_record_batch_rows.rs	New benchmark file comparing different record batch iteration approaches
src/common/recordbatch/Cargo.toml	Added criterion benchmark dependency and configuration

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[sunng87]

How will we do with the new Json type, since there is no concrete json type in datafusion?