Binary Signature Name

This proposal introduces `@BinarySignatureName` annotation that serves as a cross-platform variant of `@JvmName`
annotation that is used in Kotlin/JVM and is designed to solve various library migration and Object-C interoperability use-cases.
This annotation affects overload matching and linking of cross-platform Kotlin libraries.

For convenience of Object-C interoperability, a helper `@ObjCSignature` annotation is introduced that makes Objective-C
interoperability more straightforward as shown later.

See [binary-signature.md](https://github.com/Kotlin/KEEP/blob/binary-signature/proposals/multiplatform/binary-signature.md) for the full text of the proposal, use-cases, detailed design, and open issues. Use PR #303 for minor corrections (like typos and text style) and use this issue for the discussion on the substance of the proposal.

Read binary-signature.md for the full proposal, use-cases, detailed design, and open issues, then review the substantive discussion in this issue. PR #303 is explicitly limited to minor corrections; done means reaching agreement on the proposal's substance, and no implementation file or test is named.

Written by the indexing model from the issue text.