[IOS] Allow calling setup() multiple times

[c960657]

Some of the options provided in setup() may depend on user preferences or subscribed services.

This PR permits calling setup() again to update the settings.

[sboily]

Thanks @c960657, and sorry for the long wait. The bug is real and wider than calling setup() twice: when the app had run before, the module builds the CallKit provider from the previous launch's stored settings, so even the first setup() of a launch didn't change CallKit. I've taken your change over in #907 (you're credited as co-author), applying the configuration the same way, with one difference: a JavaScript setup() after a native [RNCallKeep setup:] stays ignored, as the README documented; calling [RNCallKeep setup:] again updates the options instead. Checked with a harness that reads the provider's configuration and on an iPhone with iOS 27 (includesCallsInRecents). I'll close this PR once #907 is merged.

[sboily]

Merged as part of #907. Thanks again!