jextract must handle "sibling" types while extracting

[ktoso]

For example file 1:

struct Hello {}

file 2:

struct HelloAgain {
  init(hello: Hello) {}
}

if we visit them in the order Hello, then HelloAgain things work fine.

If we happen to visit them HelloAgain first, then we'll reject importing the HelloAgain type because:

[info][JExtractSwift/Swift2JavaVisitor.swift:219](visit(_:)) Unable to import initializer due to unknown(IdentifierTypeSyntax
╰─name: identifier("Hello"))