chore: bring back function set_cache_capacity

[dantengsky]

I hereby agree to the terms of the CLA available at: https://docs.databend.com/dev/policies/cla/

Summary

bring back function system$set_cache_capacity (#16016)

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

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This change is 

[github-actions]

Docker Image for PR

• tag: pr-17196-ff26c0d-1736325363

note: this image tag is only available for internal use,
please check the internal doc for more details.

[github-actions]

ClickBench Report

• hits: https://benchmark.databend.com/clickbench/pr/17196/12666349631/hits.html
• internal: https://benchmark.databend.com/clickbench/pr/17196/12666349631/internal.html
• load: https://benchmark.databend.com/clickbench/pr/17196/12666349631/load.html
• tpch: https://benchmark.databend.com/clickbench/pr/17196/12666349631/tpch.html

[github-actions]

Docker Image for PR

• tag: pr-17196-53413c6-1736332879

note: this image tag is only available for internal use,
please check the internal doc for more details.

[github-actions]

ClickBench Report

• hits: https://benchmark.databend.com/clickbench/pr/17196/12668491323/hits.html
• internal: https://benchmark.databend.com/clickbench/pr/17196/12668491323/internal.html
• load: https://benchmark.databend.com/clickbench/pr/17196/12668491323/load.html
• tpch: https://benchmark.databend.com/clickbench/pr/17196/12668491323/tpch.html

[wubx]

Is there a docs for this function?

BTW:
Use system$set_cache_capacity set parameters is persistent?

[BohuTANG]

Is there a docs for this function?

BTW: Use system$set_cache_capacity set parameters is persistent?

This is used by internal not for user.

[dantengsky]

Is there a docs for this function?

BTW: Use system$set_cache_capacity set parameters is persistent?

This function is mainly designed to help cloud operators, or in private deployment scenarios, find the right cache capacity for a given workload: balancing execution performance, query soft OOM, and spill.

Once the right cache capacity is found, still need to adjust the cache size in the config to make the capacity setting persistent, ensuring it remains effective during warehouse suspend and resume operations.