Fix/validation required warning with readonly writeonly props v2

[vadyvas]

TBD:

• cli pr

What issue does this pull request resolve?

Fixes false validation warnings/errors when required is combined with readOnly / writeOnly in OpenAPI schemas—especially for request/response examples where:

• a property is required + readOnly (should be required in responses, but not required / not allowed in requests),
• a property is required + writeOnly (should be required in requests, but not required / not allowed in responses).
  This matches the real-world “single schema for input/output” use case described in validation of sample : readOnly / writeOnly and required statement interaction  redocly-cli#1416.

What changes did you make?

• Made readOnly/writeOnly context-aware validation keywords (when OAS context is provided):
  • Added lib/vocabularies/validation/readOnly.ts
  • Added lib/vocabularies/validation/writeOnly.ts
  • Registered them in lib/vocabularies/validation/index.ts
  • Removed readOnly/writeOnly from lib/vocabularies/metadata.ts so they don’t get treated as “annotation-only” -metadata (which would block validation behavior).
• Updated required validation to respect OAS request/response mode:
  • In lib/vocabularies/validation/required.ts, skips required-checks for:
    • readOnly: true properties in request context
    • writeOnly: true properties in response context
  • This only activates when the validator is called with an OAS context (via this.oas).
• Added coverage tests:
  • New spec/validation/read-write.spec.ts verifies:
    • default behavior without OAS context stays unchanged
    • readOnly rejected in request / writeOnly rejected in response (with context)
    • required skipping behavior is correct per context.

Is there anything that requires more attention while reviewing?

• Context passing is required for the new behavior: the caller must use passContext: true and call validation with a this context like { oas: { mode: 'request' | 'response', location? } }. Without it, behavior stays as before.