chore(query): Optimize hot path allocations in query formatting and metadata operations

[Copilot]

Identified and eliminated unnecessary allocations in frequently-executed code paths through targeted refactoring of string operations and collection initialization.

Changes

• Query result formatting (executor/format.rs): Replaced += &format!() with direct write!() calls to avoid intermediate String allocations in pruning statistics generation

• Metadata key operations (kv_pb_api/mod.rs): Pre-allocate result vectors with known capacity instead of growing incrementally during chunked key processing

• Key construction (key_builder.rs): Write numeric values directly to byte buffer via std::io::Write instead of allocating temporary strings

• Parser errors (parser/error.rs): Use write!() and push_str() instead of += &format!() pattern

Before:

blocks_pruning_description += &format!("range pruning: {} to {}", before, after);
let mut res = vec![];  // grows via multiple extends
self.push_raw(&format!("{}", n))

After:

write!(blocks_pruning_description, "range pruning: {} to {}", before, after).unwrap();
let mut res = Vec::with_capacity(total_keys);
write!(self.buf, "{}", n).unwrap();

These paths are executed per-query and per-metadata operation, making allocation reduction meaningful at scale.

Warning

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• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https /usr/lib/apt/methods/https --emit=dep-info,metadata -C embed-bitcode=no -C debuginfo=2 -C split-debuginfo=unpacked --check-cfg cfg(docsrs,test) --check-cfg cfg(feature, values()) n-li�� n-linux-gnu/lib/debuginfo=2 7792/build_script_build-6014bd6bab5c7792 n-linux-gnu/lib/rustlib/x86_64-REDACTED-linux-gnu/bin/rust-lld n-linux-gnu/lib//home/REDACTED/.rustup/toolchains/nightly-2025-12-11-x86_64-REDACTED-linux-gnu/bin/rustc n-linux-gnu/lib/--crate-name n-linux-gnu/lib/display_more n-linux-gnu/lib/--edition=2021 (dns block)

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Original prompt

Identify and suggest improvements to slow or inefficient code

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This change is 

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@Copilot please update it 🙏.

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## Summary

Summary about this PR

- Close #issue

[github-actions]

At least one type of change must be checked in the PR description.
@Copilot please update it 🙏.

[github-actions]

This pull request's title is not fulfill the requirements. @Copilot please update it 🙏.

Valid format:

fix(query): fix group by string bug
  ^         ^---------------------^
  |         |
  |         +-> Summary in present tense.
  |
  +-------> Type: rfc, feat, fix, refactor, ci, docs, chore

Valid types:

• rfc: this PR proposes a new RFC
• feat: this PR introduces a new feature to the codebase
• fix: this PR patches a bug in codebase
• refactor: this PR changes the code base without new features or bugfix
• ci: this PR changes build/testing/ci steps
• docs: this PR changes the documents or websites
• chore: this PR only has small changes that no need to record

[github-actions]

This pull request's title is not fulfill the requirements. @Copilot please update it 🙏.

Valid format:

fix(query): fix group by string bug
  ^         ^---------------------^
  |         |
  |         +-> Summary in present tense.
  |
  +-------> Type: rfc, feat, fix, refactor, ci, docs, chore

Valid types:

• rfc: this PR proposes a new RFC
• feat: this PR introduces a new feature to the codebase
• fix: this PR patches a bug in codebase
• refactor: this PR changes the code base without new features or bugfix
• ci: this PR changes build/testing/ci steps
• docs: this PR changes the documents or websites
• chore: this PR only has small changes that no need to record