Update Rust crate indexmap to v2.12.1

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
indexmap	dependencies	minor	2.11.4 -> 2.12.1

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Release Notes

indexmap-rs/indexmap (indexmap)

v2.12.1

Compare Source

• Simplified a lot of internals using hashbrown's new bucket API.

v2.12.0

Compare Source

• MSRV: Rust 1.82.0 or later is now required.
• Updated the hashbrown dependency to 0.16 alone.
• Error types now implement core::error::Error.
• Added pop_if methods to IndexMap and IndexSet, similar to the
  method for Vec added in Rust 1.86.

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Configuration

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[codspeed-hq]

CodSpeed Performance Report

Merging #384 will improve performances by 9.09%

_{Comparing renovate/indexmap-2.x-lockfile (349c282) with dev (68ac7fc)}

Summary

⚡ 1 improvement
✅ 5 untouched

Benchmarks breakdown

	Mode	Benchmark	BASE	HEAD	Change
⚡	Simulation	sudoku-hard	4.4 ms	4 ms	+9.09%