CycloneDX 2.0

CycloneDX 2.0 is a major version in active development, focused on cleaning up legacy constructs, enforcing semantic correctness, and enabling modern schema reuse and API integration. This issue tracks the scope, rationale, and technical direction of the 2.0 release.

### Goals
- Modularize the specification into multiple schemas (e.g. bom, component, metadata, common, etc)
- Remove deprecated fields and legacy aliases
- Constrain properties to their correct types (e.g. cryptoProperties only on cryptographic assets)
- JSON-first focus supporting JSON Schema Draft 2020-12; potentially remove XML support
- Make the schema directly usable as a canonical model for the Ecma Transparency Exchange API
- Normalize naming and structural inconsistencies

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- see milestone: https://github.com/CycloneDX/specification/milestone/2
- see release PR: https://github.com/CycloneDX/specification/pull/652