Move some test code from dbus/ and bus/ into test/
dbus currently has too much test code in bus/ and dbus/. This is awkward for several reasons:
- we need to compile the test binaries alongside the rest of bus/ and dbus/, but then run them from test/
- the test code gets counted as part of bus/ and dbus/ when computing coverage statistics, distorting our ideas about the coverage of the actual production code
- the "embedded tests" should not be compiled into libdbus and dbus-daemon when building secure, efficient production dbus binaries, but then we lose test coverage by disabling them
- the test framework used for the "embedded tests" makes it hard to skip tests that take forever and might not even be relevant to the bug/feature you're actually working on
This branch attempts to clean that up.