[instrumentation] convenience methods for chain spans

[axiomofjoy]

No description provided.

[mikeldking]

Spit balling here:

from openinference.instrumentation import agent, chain, trace


@agent(name="calculator-agent")
def agent(): 
   ....


@chain
def apply_parameters():
   ....

In addition I may want to imparatively create a span inside of a function body:

tracer = tracer_provider.get_tracer(__name__)

def some_llm_function(input):
   with tracer.start_as_current_span(
       name="name",
       kind="chain",
       attributes={},
   ) as span:
       # do work
       span.set_input(output)
       span.set_output(output)