enhance PyTorch easyblock to print individual failed tests

[Flamefire]

(created using eb --new-pr)

This enhances the output in the log file by printing not only the test suite of failed tests but also the individual failed tests. This should make it easier to determine if there is only a single test in a test suite that fails for everyone (or most) so we can disable that single test

Edit: As identified in easybuilders/easybuild-easyconfigs#18421 (comment) there are more issues with those possible solutions:

1. Patch run_test.py to not shard at all (any maybe disable the exit-on-first-failure)
2. export BUILD_ENVIRONMENT=slow-gradcheck as a hack to disable the parallelization: https://github.com/pytorch/pytorch/blob/v1.13.1/test/run_test.py#L721 although that might get forgotten when the code changes (and it seems to have changed in PyTorch 2 already and was only introduced in 1.13)
3. Make matching the test-suite-name optional for this pattern, seems to work for this example at least
4. Look into parsing the XML report (enabled via --save-xml) which might be the best option but requires quite some work.

Edit: As for 4.:
It needs 2 Python packages (i.e. builddependencies): lxml and unittest-xml-reporting and a patch for PyTorch to propagate --save-xml.
But then it has folders named after the tests with 1 or more xml files containing e.g. <testsuites><testsuite name="pytest" errors="0" failures="0" skipped="127" tests="476" time="408.891" timestamp="2023-08-16T13:49:53.750990" hostname="taurusi8002"><testcase classname="TestJitCPU" name="test_jit_alias_remapping_abs_cpu_float32" time="0.063" file="test_ops_jit.py" /> which does look helpful

[Flamefire]

@branfosj This change has been tested now multiple times and improves things. I added the possible further enhancements to the OP as found in that other build.
How to proceed?

[branfosj]

One minor change and then this is good to go. It has been well tested with various PyTorch PRs.