feat(opamp): allow configuring agent capabilities (#4897)

* feat(opamp): allow configuring agent capabilities

* docs(opamp): add changelog entry

* style(opamp): apply Ruff formatting

* fix(opamp): satisfy Pylint assertions

* Update opamp/opentelemetry-opamp-client/src/opentelemetry/_opamp/client.py

* Fix import

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Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>
Co-authored-by: Aaron Abbott <aaronabbott@google.com>