Deal with slow staging/sm tests

[ptomato]

Some of the staging/sm tests take a long time to run. For this reason the whole folder is currently omitted from test262.fyi. We should find a way to either mark particular tests as slow so that consumers can skip them if necessary, or make them less slow.

See also #3328, #1231.

[ptomato]

cc @CanadaHonk @Ms2ger

[linusg]

Relevant workaround in test262.fyi: test262-fyi/test262.fyi@8571044