[PLAT-7417] Add new APIs for removing Swift callbacks

[nickdowell]

Goal

Make it possible to remove Swift OnBreadcrumb, OnSendError and OnSession closures.

• removeOnBreadcrumbBlock not working from swift #1203

Design

When a Swift closure is passed to addOnBreadcrumb(block:) or removeOnBreadcrumb(block:) the compiler creates an NSBlock which "wraps" the closure and makes it callable from Objective-C. When Bugsnag is asked to remove a previously added callback, testing the objects for equality always fails and the original block cannot be identified in the array.

This PR makes it possible to remove closures by passing the object from addOnBreadcrumb(block:) to a new removeOnBreadcrumb(_:) function. For simplicity of implementation, addOnBreadcrumb(block:) returns the (copy of the) block that was added to the array.

The old removeOnBreadcrumb(block:) function has been marked as deprecated.

The new removeOnBreadcrumb(_:) function method accepts an AnyObject to cause a compile error if misused by passing it a closure.

Note: all this also applies to OnSendError and OnSession.

Testing

Existing unit tests amended to verify new APIs, new test cases added to verify passing invalid values to the remove: APIs.

[github-actions]

Infer: No issues found 🎉

OCLint: No issues found 🎉

Bugsnag.framework binary size increased by 18,120 bytes from 1,256,344 to 1,274,464

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