Move Agent from experimental to main

[sjrl]

Keep in mind that Agent depends on new features in:

• State (a new data class)
• updates to Tool, ComponentTool and ToolInvoker

Steps for Moving an Experiment to Haystack Core or Integrations

• Make sure the latest Haystack release or an integration release contains the merged experiment
• Update import statements in example cookbook, remove experimental tag from cookbook, etc.
• Close discussion in haystack-experimental with move information
• Remove pydocs
• Move experiment from active experiments in the catalog in haystack-experimental README.md to adopted experiments
• Remove example notebook from haystack-experimental if it exists
• feat: Add GitHub integration with agent_prompts and github_components haystack-core-integrations#1637
• add agents example with GitHub components from experimental haystack-cookbook#183

[sjrl]

Fine to move this the week of March 24th and then any remaining developments will be made directly in main.

[julian-risch]

I think it would be great to keep around https://github.com/deepset-ai/haystack-experimental/blob/main/examples/agent.ipynb somewhere but it comes with a lot of extra files so it's not our usual cookbook. Open to ideas where to move it.

Maybe https://github.com/deepset-ai/haystack-cookbook/blob/b906b92934d5fc5411295a1aa40e9303f7ab0d2f/notebooks/github_issue_resolver_agent.ipynb#L9 is enough.