Reland "[llvm-exegesis] Fix preservation of RDI in subprocess mode (#72458)"

This reverts commit 186db1bc.

This relands commit 0718c1a8.

The REQUIRES flag in the test that was added only specified that the
machine needed to have the capability to execute the snippet rather than
actually run it with performance counters. This would work with
--dummy-perf-counters, but that is not currently supported in the
subprocess execution mode. So for now, we require the ability to
actually perform measurements to prevent test failures in configurations
that don't have libpfm or access to performance counters.