Add supplier and value check

[Enkas1]

This PR adds a supplier field to license and package metadata to support SBOM generation requirements.

Changes:

• Added supplier attribute to license() and package_info() rules
• Updated LicenseInfo and PackageInfo providers to include supplier field
• Added validation requiring supplier format: "Organization: " or "Person: "
• Updated JSON output generation in both metadata gathering systems
• Added test coverage for supplier field functionality

Usage:

license(
    name = "my_license",
    supplier = "Organization: Test org",
    # ... other attributes
)

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[aiuto]

This repository is essentially abandonware, and new effort is going into work at bazel-contrib/supply-chain.
Please open an issue there, and we can start talking about the right way to do this, before sending a PR.
My quick thought is that supplier is not a feature of a license, so it should be in a different provider