test: give slow tests more time on Rasberry PIs
Refs: https://github.com/nodejs/node/issues/42379
A number of tests have been failing internmittently on the Rasberry PIs with timeouts since the update to OpenSSL 3.0. Mark them as SLOW to see if that removes the flakiness.
Signed-off-by: Michael Dawson mdawson@devrus.com