This speeds them up, and exercises the askrene parallel code.
Before: test_real_data: 348s test_real_biases: 105s
After: test_real_data: 133s test_real_biases: 106s
And this is because much of the time is spent uncompressing the gossmap
and startup.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>