Add new license bsd-3-clause-cryptogams for the CRYPTOGAMS license

[MGpromax]

Fixes #5253

Adds bsd-3-clause-cryptogams for the CRYPTOGAMS license (the BSD-3-Clause variant used by Andy Polyakov's CRYPTOGAMS cryptographic assembly modules, with an alternative clause allowing distribution under the GPL instead), using the name suggested in the issue. Text from the LICENSE file of https://github.com/dot-asm/cryptogams; SPDX has no identifier for it (checked the current license list), so spdx_license_key: LicenseRef-scancode-bsd-3-clause-cryptogams.

category: Permissive, with the GPL-alternative clause recorded in notes.

Detection before this change: the text matched bsd-new OR gpl-1.0-plus, which approximates the semantics but loses the CRYPTOGAMS identity that tools like ORT need to track these files precisely. It now detects as bsd-3-clause-cryptogams with score 100.

Validation (same for all six license additions from this batch):

• scancode-reindex-licenses runs clean
• self-detection and ignorables validation tests pass (--test-suite=validate tests/licensedcode/test_detection_validate.py), with ignorables generated by the test regen tooling rather than by hand
• pytest tests/licensedcode/test_license_models.py passes locally

Tasks

• Reviewed contribution guidelines
• PR is descriptively titled 📑 and links the original issue above 🔗
• Tests pass -- look for a green checkbox ✔️ a few minutes after opening your PR
• Commits are in uniquely-named feature branch and has no merge conflicts 📁
• Updated documentation pages (if applicable) -- not applicable
• Updated CHANGELOG.rst (if applicable) -- not applicable