[swiftsrc2cpg] Enhance inheritance handling for Swift types and xcodebuild support

[max-leuthaeuser]

We use proper fullNames now (if we have the compiler support).

Also:

• removed unused dependency from test snippets (to make them compile with both the 6.1.x and 6.2.x swift toolchain without the need to specify the SDK path).
• cleaned / refactored GsonTypeInfoReader (handles both 6.1.x and 6.2.x inheritance JSON specs).
• adjusted tests
• handle xcodebuild output correctly (for https://github.com/ShiftLeftSecurity/security-team/blob/master/vuln_iosapp/)