Investigate reducing deepcopies in Agent

[anakin87]

While reviewing deepcopy usage in Pipeline, I've also seen several deepcopies in Agent.
Worth investigating if they can be safely removed/handled differently for performance reasons.

1. agent_inputs span tags
   

   haystack/haystack/components/agents/agent.py

   Lines 755 to 756 in d12124a

   	with self._create_agent_span() as span:
   	span.set_content_tag("haystack.agent.input", _deepcopy_with_exceptions(agent_inputs))

   
   Apparently agent_inputs is created here and used for the span tag only. If that's the case, no need to deepcopy it.

2. state_schema
   

   haystack/haystack/components/agents/agent.py

   Line 292 in d12124a

   resolved_state_schema = _deepcopy_with_exceptions(self._state_schema)

   
   The goal seems to keep self._state_schema and self.state_schema separate. Would a shallow dict() copy be sufficient?

[Br1an67]

I'd like to work on this. Replaced the state_schema deepcopy with a shallow dict() copy and removed the unnecessary agent_inputs deepcopy for span tags.

PR: #10704