PCA tests fail periodically.

[KalyanovD]

Hello,
Let me bring what i have faced with during testing the functionality.

Describe the bug
It has been observed that some Catch2 tests for PCA executed with bazel sporadically fail between testing runs with lack of precision on the mean/variance calculation during training stage. An example:

During investigation it has been observed that "sporadic" fails become regular with launching tests in a single-threaded mode. This fact might be helpful for validation.

To Reproduce
Steps to reproduce the behavior:

1. Download oneDAL and bazel (bazelisk-linux-amd64)
2. bazel build //cpp/oneapi/dal/algo/pca:test_batch_host --config=host --test_link_mode=dev --test_thread_mode=par --test_external_datasets
3. taskset -c 0-0 ./bazel-bin/cpp/oneapi/dal/algo/pca/test_batch_host

Expected behavior
Tests have passed successfully.

Output/Screenshots
Screen of log with tests output.

Environment:

• OS: Ubuntu 20.04
• Compiler: GCC9.4
• Bazel: 6.3.2
• Version: latest