imp(ibc-testkit): remove field access of `MockContext`

[rnbguy]

Bug Summary

Some of the tests are written while accessing MockContext fields. Field access is discouraged over associated methods.

Details

The following should be refactored to use an associated method, e.g., MockContext::ibc_events(&self).

https://github.com/cosmos/ibc-rs/blob/d5e83145c177a2cd62135aebadaba5c9feb0fa2b/ibc-testkit/tests/core/ics04_channel/timeout.rs#L380-L385

Version

till v0.49.1