Random CI failures in xvt (part of cargotest)

[RalfJung]

#99420 failed twice with the exact same error in xvt (part of cargotest), but the third attempt worked fine. I have not checked whether this happened to other PRs, but it seems somewhat concerning.

The error is thousands of lines long and ends in

thread 'test_frequency::prop_frequency_indexed' panicked at '[quickcheck] TEST FAILED (runtime error). Arguments: (CsvData { data: [[[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[]], [[239, 187, 191]]] })
Error: "assertion failed: `(left == right)`\n  left: `[(\"(NULL)\", 60)]`,\n right: `[(\"(NULL)\", 60), (\"\\u{feff}\", 1)]`"', /cargo/registry/src/github.com-1ecc6299db9ec823/quickcheck-0.7.1/src/tester.rs:176:28

(but there is more than one assertion failure here)

[RalfJung]

Duplicate of #98068, #73514