Add customizable prefixes for CoroutinesInterop

[Kanialdo]

For some reason, the __ prefix is unacceptable for iOS developers in our team (it breaks code rules style). I would like to ask for a customization option for coroutine functions.

Current:

class B: A {
    override func __foo() async throws -> KotlinInt {
        return KotlinInt(1)
    }
}

Proposition:

Gradle:

skie {
    features {
        coroutinesInteropPrefix.set("suspend")
    }
}

Code:

class B: A {
    override func suspendfoo() async throws -> KotlinInt {
        return KotlinInt(1)
    }
}