chore: convert examples to OpenAPI v3-compliant Example Object format

[simone-stacks]

Description

Examples were not rendering correctly in some API documentation viewers (e.g., VSCode OpenAPI preview). The previous example: $ref: pattern is v2-style and not properly supported in OpenAPI v3.x.

This PR:

• Restructured all 31 OpenAPI example files to use proper Example Object format
• Converted externalValue references to $ref pattern with Example Objects
• Ensures OpenAPI v3.1 specification compliance

Applicable issues

• fixes RPC OpenApi example rendering issue #6723

Checklist

• Test coverage for new or modified code paths
• Changelog is updated
• Required documentation changes (e.g., docs/rpc/openapi.yaml and rpc-endpoints.md for v2 endpoints, event-dispatcher.md for new events)
• New clarity functions have corresponding PR in clarity-benchmarking repo

[federico-stacks]

LGMT!

Made some tests and I can confirm that the rendering issue reported in the referenced ticket seems to be solved.

[francesco-stacks]

lgtm!