GULObjectSwizzler: allow to disable generated class dispose calls.

[asafkorem]

Allow to disable generated class dispose calls explicitly, and not only when Zombies instrument is enabled.

That is, to support disabling the dispose calls in special cases which are not Zombie related, for examples: firebase/firebase-ios-sdk#9083, as suggested here.

[asafkorem]

@paulb777 @ncooke3 @maksymmalyhin tagging you guys because you were involved on the latest change on this class.

IMO this is highly important because the NSZombieEnabled variable workaround is being used from Detox, which is the end-to-end testing framework for many React Native applications. I'm afraid that using this flag may cause other side effects, like unnecessary memory consumptions or ignoring other memory issues.

I think that if we're using such workaround, at least let's have it isolated as possible.

[ryanwilson]

Thanks for the contribution! I'm good with this change. It's possible we may have to alter this in the future if we see too many reports of leaks or issues related to the flag, but we'll merge it shortly after CI passes.

[asafkorem]

Thanks guys @paulb777 @ryanwilson!