Add xctrunnertool to create test bundles

[kapoorlakshya]

In Progress...

Usage

load("//apple:xctrunner.bzl", "xctrunner")

ios_ui_test(
    name = "HelloWorldSwiftUITests",
    minimum_os_version = "15.0",
    runner = "@build_bazel_rules_apple//apple/testing/default_runner:ios_xctestrun_ordered_runner",
    test_host = ":HelloWorldSwift",
    deps = [":UITests"],
)

xctrunner(
    name = "HelloWorldSwiftXCTRunner",
    test_targets = [":HelloWorldSwiftUITests"],
    testonly = True,
)