Revive Ballerina OpenAI images connector

[NipunaRanasinghe]

Description: To align with the new Ballerina connector reviving effort, we need to update the existing Ballerina OpenAI Images connector(https://central.ballerina.io/ballerinax/openai.images/1.0.5) to comply with the Ballerina standard connector development process and support the latest OpenAI API versions in Ballerina.

Following high-level tasks should be completed with this effort:

• [x] Create a new repository + setup the project structure and workflows
• [x] Sanitize the OpenAPI spec (if needed) and, generate the client connector
• [x] Implement a test suite for the connector
• [x] Improve the documentation with setup guide and quickstart guide
• [x] Add example usecase for the connector

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[NipunaRanasinghe]

Closing as the new version is released in the central