workflows: Add clang format check workflow.

[soburi]

Cherry-pick the commit adding .clang-format from https://github.com/arduino/ArduinoCore-zephyr.

[Copilot]

Pull request overview

This PR adds automated clang-format checking to the CI pipeline by cherry-picking configuration from the ArduinoCore-zephyr repository. The workflow will run on code changes to C/C++ files and enforce consistent code formatting across the project.

• Adds GitHub Actions workflow for automated clang-format validation
• Introduces comprehensive clang-format configuration based on LLVM style with Zephyr-specific customizations
• Configures format checking for specific project directories (cores/arduino, loader, libraries) with selective exclusions

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
.github/workflows/format_check.yml	New workflow that triggers format checks on C/C++ file changes using clang-format v19 across multiple project directories
.clang-format	Configuration file defining LLVM-based formatting rules with Zephyr macros, 100-column limit, and project-specific style preferences

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[Copilot]

The matrix configuration has duplicate 'exclude' keys. In YAML, when the same key appears multiple times at the same level, only the last value is retained. This means only 'ea_malloc' will be excluded, and the 'loader/llext_exports.c$' and 'examples' exclusions will be ignored. These should be combined into a single exclude pattern using regex alternation, or the matrix structure should be redesigned to support multiple exclusions per path.

Suggested change

	exclude: 'examples'
	exclude: 'extras'
	exclude: 'ea_malloc'
	exclude: 'examples|extras|ea_malloc'

[Copilot]

There is trailing whitespace after 'Log level' on this line. This should be removed to maintain consistent code formatting.

Suggested change

	description: 'Log level'
	description: 'Log level'

[DhruvaG2000]

I know this is just a cherrypick, but it would still be better if you added your SoB, since you are the one cherrypicking it to this project.
Also amend the commit body to contain something useful and resolve the github copilot review issues.
Thanks!

[DhruvaG2000]

These folders don't exist in this project, cleanup to remove irrelevant stuff.

[soburi]

I think this will be added as the integration with the Arduino repository progresses, so I would like to leave it as it is as long as it doesn't cause any errors.