… r=alexcrichton

Relaxes expectation of `cargo test` tests to accept test execution time

rust-lang/rust#75752 changes the output of libtest.

For example, output before:

```
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
```

Output after:

```
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.01s
```

This breaks some cargo tests: https://github.com/rust-lang-ci/rust/runs/1439245145

As a preparation for the merge, this PR relaxes the test expectations of `cargo test` tests to accept both outputs. I'm using the existing pattern feature of `Execs::with_stdout`:

```
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out[..]
```

I made this change for the following tests:

- `test::can_not_mix_doc_tests_and_regular_tests`
- `test::cargo_test_quiet_with_harness`
- `test::test_filtered_excludes_compiling_examples`
- `test::cargo_test_doctest_xcompile_ignores` (didn't fail in rust-lang/rust#79317, but failed locally)
- `test::cargo_test_doctest_xcompile` (doesn't run locally, I changed it just to be safe)
- `test::cargo_test_doctest_xcompile_runner` (doesn't run locally, I changed it just to be safe)
- `test::cargo_test_doctest_xcompile_no_runner` (doesn't run locally, I changed it just to be safe)

If requested, I will open another PR later to change the expectation to:

```
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in [..]s
```

However, I don't know how to handle WASM targets because WASM doesn't support time measuring, therefore the libtest output didn't change for WASM. Is WASM even relevant here?