Refactor efi/preinstall

[frederic-hoerni]

This modification refactors part of efi/preinstall to reduce duplicated code in tests and split Run() into smaller functions.

It also adds license, readme and makefile to give a little more context about secboot.

[pedronis]

small naming comment

[Copilot]

Pull request overview

This PR refactors parts of efi/preinstall to reduce test duplication and simplify error/action handling in RunChecksContext, while also adding top-level project metadata (license/readme/make targets) to improve repo usability.

Changes:

• Extracts error classification/action derivation into RunChecksContext.convertErrorsToActions and simplifies Run() control flow.
• Deduplicates a large amount of preinstall test setup by introducing shared mock MEI fw_status constants and a shared default EFI image set.
• Adds README.md, COPYING, and a Makefile with convenient build/test/coverage targets; increases run-tests timeout.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
run-tests	Extends go test timeout to 30m.
README.md	Adds a brief project overview, features list, and license pointer.
Makefile	Adds build + test convenience targets, including focused efi/preinstall coverage runs.
internal/efitest/wincert.go	Splits Authenticode detached win-cert creation into a reusable base helper and adds “must” variant.
efi/preinstall/preinstall_test.go	Precomputes a reusable WinCertificate instance for tests.
efi/preinstall/intel_mei_test.go	Introduces shared mock fw_status register encodings for MEI/BootGuard tests.
efi/preinstall/efi_images_test.go	Adds shared default mock EFI images + digests for tests.
efi/preinstall/checks_test.go	Switches many tests to use shared MEI fw_status data and shared default images.
efi/preinstall/checks_context.go	Refactors RunChecksContext.Run() by extracting error→actions conversion logic.
efi/preinstall/check_pcr7_test.go	Uses shared digest constants to reduce repetition.
efi/preinstall/check_pcr4_test.go	Uses shared digest constants to reduce repetition.
efi/preinstall/check_host_security_intel_test.go	Uses shared MEI fw_status test vectors.
efi/preinstall/check_host_security_amd64_test.go	Uses shared MEI fw_status test vectors.
COPYING	Adds GPLv3 license text.

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[pedronis]

@frederic-hoerni thanks for splitting the refactorings, some of the copilot comments seemsat least worth answering to

[frederic-hoerni]

I took into account the remarks. I will squash the relevant commits when all will be approved.

[pedronis]

thank you