create check-exposure-has-meta-keys

[damiantl]

Describe the feature you'd like With the addition of exposures, apart from models and sources, it would be great to have a hook to check if they have meta keys defined or not. Like for example the check-model-has-meta-keys or check-source-has-meta-keys we already have.

Similar to what we have for models with the "--allow-extra-keys" flag, might be also very intersting to have for exposures.

Additional context This would be really useful to enforce exposure governance.