Prototype Bazel-native FOSS tests

[nettle]

Why:
The existing Python/Bash FOSS tests are hard to
understand and extend, they are also very slow
and cannot be integrated into Bazel environment.

What:
Add test/bazel/ with a foss_test() macro
that generates py_test() targets for FOSS projects.

Test:
bazel test //test/bazel/...

[nettle]

Hi @furtib and @Szelethus,
I had a few minutes to demo Bazel approach for tests,
so please take a look - this is just very simple idea for FOSS tests.

[furtib]

I like the idea, haven't thought of it in this way.
But why do it in a separate folder?
(minor note, due to how the CI is set up, it doesn't actually run these tests)
It also does not work on the Bazel 6 version, since we don't use the WORKSPACE file at all.

Just now I realized, tests is only used to disable the per-file test in yaml-cpp?

Let me show what I'm thinking of. (tomorrow...)

[Szelethus]

I like the approach! Would it be okay if, while preserving the main idea, we polished the PR up?

[nettle]

The approach is actually questionable - run bazel from bazel.
So we should consider it very carefully.

Anyway, I have 2 conclusions in mind:

1. We should develop bazel tests instead of python tests
2. Even running bazel from bazel is better than bazel from python

[Szelethus]

Sure! Lets think of a solution that is actionable and can be implemented incrementally. I don't mean this to come off the wrong way, but our bazel 8 support project showed how striving for perfection was the enemy of progress.

Our foss tests so far have borne some fruit, even if they are imperfect.

[Szelethus]

Now that we are through the prototype phase, I suppose this can just replace the existing FOSS tests, right?

Also, whats the rationale behind the test/bazel/ directory instead of test/foss?

[furtib]

To bring all FOSS into Bazel discussion here:
This PR in particular is good in terms of performance (~3x quicker than others). Other prototypes/experiments (#300 and #235) have extremely poor performance.

[nettle]

Now that we are through the prototype phase, I suppose this can just replace the existing FOSS tests, right?

Also, whats the rationale behind the test/bazel/ directory instead of test/foss?

Agree, I will replace tests in test/foss with these bazel tests.

[nettle]

To bring all FOSS into Bazel discussion here: This PR in particular is good in terms of performance (~3x quicker than others). Other prototypes/experiments (#300 and #235) have extremely poor performance.

Basically this is just setUpClass vs setUp bug.
I've left a comment in #300