Perf: Optimize function TwoLevelIterator::Seek in table/two_level_iterator.cc

[fyrsta7]

Summary

This PR optimizes the performance of the function TwoLevelIterator::Seek in table/two_level_iterator.cc.
Performance was measured using the project's standard benchmark tools. Out of 22 test cases, the optimization achieves a maximum improvement of 68.56% while guaranteeing no regression exceeds 1.56% in any other case.

Test Plan

1. Correctness: All existing unit tests pass.
2. Performance: A comprehensive performance evaluation was conducted using the built-in db_bench tool. The automated script covers several key aspects of database performance, ensuring no regressions and evaluating the impact of the changes under various workloads. The specific benchmarks executed include:
   1. Core Read/Write Operations
   2. Concurrency and Database Management
   3. Configuration Impact: Compared random write performance with different value sizes (100 bytes vs. 1KB) to understand the impact on throughput.

Performance Evaluation & Results

Testing Protocol:

• The benchmark was run on an isolated Ubuntu 24.04 server.
• The first run was discarded to account for cold-start effects.
• The results below are the average of 5 subsequent runs.
• The improvement for a test case is calculated as (new_value - old_value) / old_value * 100% if a higher value is better (e.g., throughput), or (old_value - new_value) / new_value * 100% if a lower value is better (e.g., latency). A positive percentage indicates a performance gain.

Results:

Test Case	Improvement
section_1_core_read_write.1_2_fillrandom.throughput_mb_s	-0.23%
section_1_core_read_write.1_6_overwrite.throughput_mb_s	0.12%
section_1_core_read_write.1_3_readseq.throughput_mb_s	0.92%
section_1_core_read_write.1_1_fillseq.throughput_mb_s	-0.26%
section_1_core_read_write.1_6_fillrandom.throughput_mb_s	0.42%
section_1_core_read_write.1_2_fillrandom.micros_per_op	-0.31%
section_1_core_read_write.1_6_overwrite.micros_per_op	0.13%
section_1_core_read_write.1_4_readrandom.micros_per_op	-0.46%
section_1_core_read_write.1_5_seekrandom.micros_per_op	68.56%
section_1_core_read_write.1_3_readseq.micros_per_op	0.96%
section_1_core_read_write.1_1_fillseq.micros_per_op	-0.38%
section_1_core_read_write.1_6_fillrandom.micros_per_op	0.42%
section_2_concurrent_compression.2_2_fillrandom.micros_per_op	1.67%
section_2_concurrent_compression.2_1_readwhilewriting.micros_per_op	5.54%
section_2_concurrent_compression.2_2_compact.micros_per_op	1.30%
section_2_concurrent_compression.2_3_fillsync.micros_per_op	-1.56%
section_2_concurrent_compression.2_2_fillrandom.throughput_mb_s	1.71%
section_2_concurrent_compression.2_3_fillsync.throughput_mb_s	0.00%
section_3_config_comparison.3_1_fillrandom_small.micros_per_op	0.38%
section_3_config_comparison.3_2_fillrandom_medium.micros_per_op	-0.20%
section_3_config_comparison.3_1_fillrandom_small.throughput_mb_s	0.35%
section_3_config_comparison.3_2_fillrandom_medium.throughput_mb_s	-0.23%

[fyrsta7]

Could a maintainer please approve the workflow to run? Thanks!