Filter out `$suspendImpl` functions declared in interfaces

[fzhinkin]

On JVM, the compiler generates special <original function name>$suspendImpl methods for every open suspendable function. For classes, these methods are package private and are never included in dump. For interfaces, however, such functions could only be either private (but we need to call them outside the interface, so that doesn't work), or public (we are here now). So, these public functions do not constitute the public ABI and are public only due to restrictions imposed on class files.

BCV should filter these methods out of generated dumps.

[fzhinkin]

See Kotlin/kotlinx.coroutines#4244 for example of a dump with $suspendImpl functions.