Deprecate `State`from haystack.dataclasses

[Amnah199]

Summary and motivation

State is removed from haystack.dataclasses and moved to agents.state in this PR and needs to be deprecated in Haystack 2.16.0. On the side, we also need to remove as merge_lists and replace_value methods from state_utils are deprecated as well.

Checklist

Tasks

• [ ] The changes are merged in the main branch (Code + Docstrings)
• [ ] Release notes have documented the breaking change
• [ ] A new version of haystack-ai has been released on PyPI
• [ ] Docs at https://docs.haystack.deepset.ai/ were updated
• [ ] Integrations on haystack-core-integrations were updated (if needed) - This step might require a Breaking change proposal on the repo
• [ ] Notebooks on https://github.com/deepset-ai/haystack-cookbook were updated (if needed)
• [ ] Tutorials on https://github.com/deepset-ai/haystack-tutorials were updated (if needed)
• [ ] Articles on https://github.com/deepset-ai/haystack-home/tree/main/content were updated (if needed)
• [ ] Integration tile on https://github.com/deepset-ai/haystack-integrations was updated (if needed)