bitbake: toaster: Add toaster-tests-requirements.txt to add pytest and some plugins

The pytest framework makes it easy to write small, readable tests, and can scale
to support complex functional testing for applications and libraries.
- Pytest-html is a plugin for pytest that generates a HTML report for test results.
- Pytest-django allows us to test Django project/applications with the pytest testing tool.
- Pytest-env is a pytest plugin that enables us to set environment variables in a pytest.ini or pyproject.toml file
- Pytest-metadata is a plugin for pytest that provides access to test session metadata, required by pytest-html plugin
to provides metadata information in the HTML report like below:

Python 3.10.12
Platform Linux-6.2.0-35-generic-x86_64-with-glibc2.35
Packages:
    - pytest: 7.4.2
    - pluggy: 1.3.0
Plugins	:
    - django: 4.5.2
    - metadata: 3.0.0
    - order: 1.1.0
    - html: 4.0.2
    - env: 1.1.0

To make difference between bitbake and toaster python requirements,
a dedicated requirements file is created for toaster in root of toaster dir.

(Bitbake rev: 804d17df22391b2d18a68d8cb05a04841d4e551b)

Signed-off-by: Alassane Yattara <alassane.yattara@savoirfairelinux.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/toaster/tests/toaster-tests-requirements.txt

@@ -1 +1,6 @@
 selenium>=4.13.0
+pytest==7.4.2
+pytest-django==4.5.2
+pytest-env==1.1.0
+pytest-html==4.0.2
+pytest-metadata==3.0.0