ci: Raise the timeout multipliers for jobs that run in QEMU

For individual tests in dav1d-test-data, the default timeout is 30 seconds (which is the Meson default if nothing is specified). Previously it ran with a multiplier of 4, resulting in a total timeout of 120 seconds.

When running tests in QEMU, exceeding this 120 second timeout could happen occasionally. Raise the multiplier to 10, allowing each individual job to run for up to 5 minutes.

This should hopefully reduce the amount of stray failures in the CI.

For tests that already have a higher default timeout set, such as checkasm which has got a 180 second default timeout, this results in a much longer timeout period. However as long as we don't frequently see issues where these actually hang, it should be beneficial to just let them run to completion, rather than aborting early due to a tight timeout.