Feature: Add the generate_pkgid_to_licenses() function for retrieving the licenses for artifacts

[DilumAluthge]

Motivation

Currently, PackageAnalyzer.jl offers the ability to process a Manifest.toml and extract the licenses for all of the Julia packages.

However, many Julia packages use binary artifacts, and the licenses for those binary artifacts may often differ from the license of the Julia wrapper.

This PR adds the ability to extract the licenses for the binary artifacts.

Example usage

import PackageAnalyzer

Pkg.activate("/path/to/my/project")
Pkg.instantiate()
Pkg.precompile()

my_manifest = "/path/to/my/project/Manifest.toml"

all_pkgs = PackageAnalyzer.find_packages_in_manifest(my_manifest)
jll_pkgs = filter(x -> endswith(x.name, "_jll"), all_pkgs)


artifact_hash_to_licenses = Dict{Base.SHA1,Vector{PackageAnalyzer.ArtifactLicenseInfo}}()

PackageAnalyzer.generate_artifact_hash_to_licenses!(
    artifact_hash_to_licenses,
    jll_pkgs;
    allow_no_artifacts=Base.PkgId[],
)

pkgid_to_licenses = PackageAnalyzer.artifact_license_map(
    jll_pkgs,
    artifact_hash_to_licenses;
    allow_no_artifacts=Base.PkgId[],
)

[DilumAluthge]

@ericphanson @giordano: Would you be able to review this?