Move to CDDL - main schema

[rmarx]

This PR bundles the TypeScript-to-CDDL changes for draft 0.4 for the main schema document (see other PRs for the QUIC and H3/QPACK documents).

List of intended changes:

• Replace TypeScript with CDDL descriptions
• Split up CDDL definitions and JSON examples
• Properly explain the $ProtocolEventBody extension point + include trigger in the example
• Properly discuss how event docs should define triggers in the CDDL
• Replace TypeScript explanation in Notational Conventions and qlog to JSON mapping with CDDL and I-JSON references, basic explanations and considerations.
• Refer to main schema CDDL introduction in H3 and QUIC docs as well
• Explain the need for custom uint64 and hexstring CDDL types
• Add uint32, uint16 and uint8 types
• Add $ProtocolEventBody listings in the QUIC and H3 docs as well!
• Update QUIC and H3 docs to use uint32 instead of normal uint