Don’t include module name in test IDs

[ahoppen]

Determining the module name of a test in the syntactic test scanner requires us to get build settings, which can be slow while the build system generates the build graph. With #1662, I don’t think it’s necessary to include the module name in the test ID anymore to differentiate test suites with the same name in different modules.

[ahoppen]

Synced to Apple’s issue tracker as rdar://137886483