Relax context annotation constraint on op/asset fn params

[benpankow]

Summary

Motivated by https://github.com/dagster-io/dagster/issues/18924.

Relaxes the annotation constraints on context to accept subclasses of OpExecutionContext, AssetExecutionContext.

Test Plan

New unit test.

[benpankow]

• #18941 👈 (View in Graphite)
• master

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