testsuite: use SysprofProfiler for profiling

testsuite: use SysprofProfiler for profiling

Instead of using sysprof-cli to profile subprocesses, this uses
libsysprof's SysprofProfiler directly so that we can avoid an indirect
subprocess as well as disabling the polkit nag.

To do this, we have to link against libsysprof instead of
libsysprof-capture. This is limited to the -Dbuild-tests=true and
-Dprofiler=true case.