[2.0]: fix unreachable cross-references

[jkowalleck]

in CycloneDX 2.0 we have unreachable cross-references

• specification/schema/2.0/model/cyclonedx-license-2.0.schema.json

  Line 128 in 2a86067

  "$ref": "../spdx.schema.json",

• specification/schema/2.0/model/cyclonedx-cryptography-2.0.schema.json

  Line 97 in 2a86067

  "$ref": "../cryptography-defs.schema.json#/definitions/ellipticCurvesEnum",

• https://github.com/CycloneDX/specification/pull/678/changes#r3685780638
• to be continued

main goal

have these links fixed

additional goal

have a tool that checks all those $ref values

• minimum: that start with a . and see if they exist - not only the file, but also the linked element
• maximum: any value and see if the linked element exists - in the remote document (starts with ./ or ../) or the same document (start with #) ...

hm, Our validators that test weather the test cases are schema-valid should have picked this up already ...
let's see why they did not