Add support for Opaque Objects #1

Job	Run time
build_and_test_with_default_features (beta)	32s
build_and_test_with_default_features (stable)	34s
build_and_test_with_default_features (1.88.0)	32s
build_and_test_with_extra_features (stable, --no-default-features --example demo --features tls-w...	32s
build_and_test_with_extra_features (stable, --no-default-features --features sync)	35s
build_and_test_with_extra_features (stable, --no-default-features --example demo --features tls-w...	56s
build_and_test_with_extra_features (stable, --features tls-with-rustls --example demo)	38s
build_and_test_with_extra_features (stable, --no-default-features --example demo --features tls-w...	35s
build_and_test_with_extra_features (stable, --no-default-features --example demo --features tls-w...	33s
build_and_test_with_extra_features (stable, --features tls-with-openssl --example demo)	36s
build_and_test_with_extra_features (stable, --no-default-features --features async-with-tokio)	35s
	6m 38s

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