Random-seed-dependent test failures in `macOS pylatest_conda_forge_arm` job

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While using the `[all random seeds]` commit-message marker in #32582, I noticed that some tests can fail under certain seeds. The failures appear in the `macOS pylatest_conda_forge_arm` job.

The CI failure can be found here: https://github.com/scikit-learn/scikit-learn/actions/runs/19417674441/job/55549227614?pr=32582

In particular, the following tests are affected:

<details>
<summary>
<code>affected_test[random_seed]</code>
</summary>

```bash
covariance/tests/test_graphical_lasso.py::test_graphical_lassos[95]
covariance/tests/test_robust_covariance.py::test_mcd
covariance/tests/test_robust_covariance.py::test_mincovdet_bias_on_normal[42-2000-10]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[6]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[14]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[19]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[23]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[30]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[32]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[37]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[47]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[50]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[55]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[61]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[64]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[67]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[72]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[79]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[80]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[88] 
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[93]
tree/tests/test_tree.py::test_absolute_errors_precomputation_function[94]
```
</details>

This can be reproduced by:

1. Using the `[all random seeds]` commit-message marker (see [here](https://scikit-learn.org/stable/developers/contributing.html#commit-message-markers)), or
2. Setting the environment variable on macOS (see [here](https://scikit-learn.org/stable/computing/parallelism.html#sklearn-tests-global-random-seed)):

```bash
$ export SKLEARN_TESTS_GLOBAL_RANDOM_SEED="all"
```

At first glance, the failures come from `assert_allclose`, so tweaking the `rtol` or `atol` in those tests should address the issue. This will need to be verified by pushing a commit with the `[all random seeds]` marker and letting the CI run to completion, which usually takes about two hours.

Edit: add more failed tests

COMMENT:
In the end, I managed to reproduce the bug for `covariance/tests/test_robust_covariance.py::test_mincovdet_bias_on_normal` so I opened the PR too.

So in total, I opened 4 PRs for the 4 tests. They are all ready for review 😄

Labels: Bug, module:test-suite, OS:macOS