Block arguments decorated w/ NS_NOESCAPE where appropriate

[gcox]

Resolves: #175

Objective-C closures are implicitly escaping, Swift closures are implicitly non-escaping 🤦‍♂️

For Swift projects using YapDB, if you create a func that has a closure argument, and that closure is then passed to a YapDB method (e.g. to synchronously enumerate something), you'll need to mark that closure as escaping, even though the method you're calling doesn't actually need it to be escaping.

Decorating the Objective-C block arguments w/ NS_NOESCAPE clarifies to the caller that no, the thing you're calling will not be hanging onto the closure you're passing it. Unless it's asynchronous, or the closure is actually stored (e.g. group blocks/sorting blocks/search handler blocks/etc), it doesn't need to be escaping.

[robbiehanson]

Very cool. Thank you!