Implement integration tests that confirm specific Xcode versions work

The project aims to define a matrix of Bazel versions and Xcode versions that work with rules_xcodeproj. The integration tests should exercise a basic set of functionality for each supported combination. As a general rule, the project will support the latest Xcode version, the previous release and the last major release. As of the writing of this issue, those versions are:

• Latest: 13.3
• Previous: 13.2.1
• Previous Major: 13.0

NOTE: The supported Bazel versions are already defined in //:bazel_versions.yml.

• Create a file/macro that defines the supported Xcode versions.
• Update the ios_app integration test to execute the supported combinations.