Replace torch.op(x) with x.op() for speed

[jank324]

Description

Sub- / replacement PR for #538.

Calling x.op() seems to be marginally but consistently faster than torch.op(x).

Motivation and Context

• I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)

Checklist

• I have updated the changelog accordingly (required).
• My change requires a change to the documentation.
• I have updated the tests accordingly (required for a bug fix or a new feature).
• I have updated the documentation accordingly.
• I have reformatted the code and checked that formatting passes (required).
• I have have fixed all issues found by flake8 (required).
• I have ensured that all pytest tests pass (required).
• I have run pytest on a machine with a CUDA GPU and made sure all tests pass (required).
• I have checked that the documentation builds (required).

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[jank324]

[Copilot]

Pull Request Overview

This PR replaces torch.op(x) function calls with x.op() method calls throughout the codebase for marginal but consistent performance improvements. The changes affect mathematical operations like sqrt(), sin(), cos(), abs(), sum(), any(), and others across the entire codebase.

Key changes include:

• Replacing torch.sqrt(x) with x.sqrt(), torch.sin(x) with x.sin(), etc.
• Replacing torch.sum(x) with x.sum(), torch.any(x) with x.any()
• Renaming function parameters from input to inputs for consistency in statistics utilities
• Adding documentation to CONTRIBUTING.md with examples of the faster patterns

Reviewed Changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/test_statistics.py	Updated test assertions to use .isnan() method
tests/test_space_charge_kick.py	Replaced torch math functions with tensor methods in test calculations
tests/test_cavity.py	Updated assertions to use tensor methods
cheetah/utils/statistics.py	Replaced torch functions with tensor methods; renamed parameters from input to inputs
cheetah/utils/physics.py	Replaced torch.sqrt() with .sqrt()
cheetah/utils/kde.py	Replaced torch functions with tensor methods
cheetah/utils/bmadx.py	Replaced torch math and utility functions with tensor methods
cheetah/track_methods.py	Replaced torch functions with tensor methods in transfer map calculations
cheetah/particles/particle_beam.py	Replaced torch functions with tensor methods throughout beam calculations
cheetah/particles/parameter_beam.py	Replaced torch functions with tensor methods in parameter beam
cheetah/particles/beam.py	Replaced torch functions with tensor methods in base beam class
cheetah/converters/bmad.py	Updated phase calculation to use .rad2deg() method
cheetah/accelerator/*.py	Replaced torch functions with tensor methods across all accelerator elements
CONTRIBUTING.md	Added documentation for the faster operation patterns
CHANGELOG.md	Updated changelog to reference this PR

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