Issue Description:

When executing tests using the SwiftPM, the code coverage results include all targets (including testing and dependencies targets).

Using an Xcode project I can configure a scheme to gather coverage for some targets only. But there's no such option when executing tests with SwiftPM.
It would be useful if we could configure which targets to include in code coverage results and have feature parity with xcodebuild.

This has also been discussed in https://forums.swift.org/t/gather-coverage-for-some-targets-with-swift-packages/31142.