Has Hawking radiation and black hole evaporation been observed by astronomers?
Has Hawking radiation ever been observed or has there been any attempt of observing them?
No, it has never been detected. The Hawking radiation from a stellar-mass black hole is so weak that it can never be detected by any foreseeable technology.
Moreover, Hawking radiation causes a black hole to evaporate. Is there any hint in astronomy for the occurrence of such events?
No. Any stellar-mass black hole that has existed in the universe so far will have been absorbing mass-energy faster than it lost it through Hawking radiation, even if the only infalling energy was from the cosmic microwave background.
Are there chances of observing them in future in the sense that are there people/collaborations who dedicatedly looking for Hawking radiation?
The only realistic possibility I've seen suggested was that in some scenarios involving large extra dimensions, the LHC could have produced microscopic black holes. Microscopic black holes could evaporate relatively quickly, and the radiation might be detectable. However, they don't seem to have been produced at the LHC.