Introduce REST API Endpoints for Agents

[tmichaeldb]

Description

See Agent design doc for more context.

To support agents on the backend, we need to be able to perform CRUD operations on them from the frontend. This PR introduces the following endpoints:

• GET /projects/<project_name>/agents (Gets all agents in a project created by the user)
• GET /projects/<project_name>/agents/<agent_name> (Gets an agent in a project by name)
• PUT /projects/<project_name>/agents/<agent_name> (Updates an agent in a project, creating it if it doesn’t already exist)
• POST /projects/<project_name>/agents (Creates a new agent in a project)
• DELETE /projects/<project_name>/agents/<agent_name> (Deletes an agent in a project by name)

Closes #7221

Type of change

• ⚡ New feature (non-breaking change which adds functionality)
• 📄 This change requires a documentation update

Verification Process

To ensure the changes are working as expected:

• Test Location: tests/api/http/agents_test.py
• Verification Steps: python -m pytest .\tests\api\http\agents_test.py

Checklist:

• My code follows the style guidelines(PEP 8) of MindsDB.
• I have appropriately commented on my code, especially in complex areas.
• Necessary documentation updates are either made or tracked in issues.
• Relevant unit and integration tests are updated or added.

[yuhuishi-convect]

🆗