Allow custom access modifiers for alias

[p-x9]

Currently, the original access modifier is carried over to the alias.

@Alias("こんにちは")
public var hello: String = ""
// ↓ expand
public var こんにちは: String {
    get { hello }
    set {  hello = newValue }
}

I would like to be able to specify access modifiers for aliases as follows

@Alias("こんにちは", access: .private)
public var hello: String = ""
// ↓ expand
private var こんにちは: String {
    get { hello }
    set {  hello = newValue }
}