Lemoncheesecake

- **ReportPortal**:
- add support for ReportPortal 5.x (4.x is no longer supported)
- steps are now logged as "nested steps" in ReportPortal
- **xml** and **junit** reporting backends now use the builtin XML implementation of Python, making it possible
to drop the lxml dependency (it caused some installation difficulties in some cases/platforms);
as a result, the `xml` and `junit` installation "extras" no longer exist (using them with `pip install` will simply
trigger a warning)
- Add support for Python 3.12
- Drop support for Python 3.7

- Teardown fixtures of the same scope in the LIFO order

- `lcc run --save-report every_Ns`: fix option no longer working (bug introduced in 1.14.1)

- `lcc.depends_on()`: the decorator argument can now be expressed as a callable that acts like a filter
- `lcc check`: improve coherency checks
- `lcc run --save-report every_Ns`: compute the time interval using the time the report has been
actually saved

- **CLI**: add a `lcc check` command to check the project validity
- **doc (http://docs.lemoncheesecake.io)**: use Sphinx 5.0.0 and improve type hinting
- Add official support for Python 3.11
- Drop support for Python 2.7 and upgrade/cleanup the whole code base to take advantage
of being Python 3.7+ only

- **HTML report**:
- upgrade bootstrap and bootswatch-slate theme from 3.3.6 to 5.1.3
- use bootstrap-icons over fontawesome
- many visual improvements among which:
- move all controls to a new fixed top-navbar
- make the report content more readable by increasing font size and contrast
- Drop Python 3.6 support