[base-controller] Add RestrictedControllerMessenger tests for runtime error handling

[MajorLift]

Explanation

• Previously, error handling branches for RestrictedControllerMessenger methods were not being tested on the basis of compile-time checks: "Branches unreachable with valid types".
• However, given that these methods are being called by our JavaScript clients, we also need assurances on runtime error-handling behavior.
• This PR adds jest tests for the previously ignored error handling branches: coverage is brought up to 100%.
• @ts-expect-error is used to suppress the compile-time type errors to simulate a JavaScript environment.

References

• Closes [base-controller] Add RestrictedControllerMessenger tests for runtime error handling #2059
• See [base-controller] Enforce that RestrictedControllerMessenger is not initialized with internal actions/events in allow lists #2051 (comment)

Changelog

@metamask/base-controller

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've highlighted breaking changes using the "BREAKING" category above as appropriate

[mcmire]

One thing, but otherwise looks good.

[mcmire]

Doesn't registerActionHandler take two arguments? Should the // @ts-expect-error be added above the action not above the method call?

Suggested change

	// @ts-expect-error suppressing to test runtime error handling
	restrictedControllerMessenger.registerActionHandler(
	'CountController:count',
	);
	restrictedControllerMessenger.registerActionHandler(
	// @ts-expect-error suppressing to test runtime error handling
	'CountController:count',
	() => {
	// do nothing
	}
	);

[MajorLift]

Good point! Fixed here 42a614e

[mcmire]

Great!