Handle breaking changes when upgrading the Xcode/SDK version?

[madsmtm]

In #334 there were exactly two breaking changes:

• The signature of NSDiffableDataSourceSnapshot::appendSectionsWithIdentifiers was changed (added correct array type).
• ASWebAuthenticationSessionWebBrowserSessionManager::registerDefaultsForASWASInSetupAssistantIfNeeded was removed

Which would definitely have been possible to stub out, and avoid it being a breaking change.

But do we want to? Or would we expect this functionality to be so rarely used, if ever, that it goes under "acceptable breakage"?

(Not really that important to figure out yet, since icrate is quite far from finished. But still important to do at some point!)

[madsmtm]

In #762, I've decided to accept a bit of breakage in rarely used crates, but have made workarounds to avoid breaking changes in e.g. objc2-metal.

I find it likely that's going to be my approach going forwards as well (though when a crate is popular enough to get special treatment is still a hard tradeoff).