fix(js/core): fix ValidationResponse type and cache ajv validators

[7hokerz]

Description here... Help the reviewer by:

• Fixed validateSchema function to return ValidationResponse instead of using the previously unused type.
• Enabled caching via ajvValidators in the validation process.
• This changes Improve type safety by repurposing the previously unused ValidationResponse as the fixed return type for validateSchema

Checklist (if applicable):

• PR title is following https://www.conventionalcommits.org/en/v1.0.0/
• Tested (manually, unit tested, etc.)
• Docs updated (updated docs or a docs bug required)

[gemini-code-assist]

Code Review

This pull request refactors the schema validation logic in js/core/src/schema.ts, including renaming the AJV validator cache and error mapping functions, and updating the ValidationResponse type for improved clarity. The validateSchema function was updated to better handle caching and return structures. Feedback highlights a potential TypeError when using boolean schemas as WeakMap keys, the need for safer handling of optional error messages in AJV, and the importance of maintaining safety checks when processing validation errors.