Pysdm

- new example notebooks and smoke tests covering complete set of figures from [Grabowski & Pawlowska 2023](https://doi.org/10.1029/2022GL101917)
- new product base class: `_ActivationFilteredProduct`
- new products based on the above: `ActivatedParticleConcentration`, `ActivatedParticleSpecificConcentration`, `ActivatedMeanRadius`
- new size-spectral products: `MeanVolumeRadius`, `AreaStandardDeviation`, `RadiusStandardDeviation`, `VolumeStandardDeviation`
- new attribute: `EquilibriumSupersaturation`
- cleanups in `Yang_et_al_2018` example (incl. using the above new products instead of manually computing the activation-filtered quantities)

kudos AgnieszkaMakulska!

- switching from "n" to "multiplicity" for attribute key (1123)
- improving reporting of filenames in pytest example test suites (1121)

- linear (instead of constant) density/pressure profile for condensation in parcel environment (kudos mikhailmints)
- updates in immersion freezing example to match [arXiv-uploaded](https://arxiv.org/abs/2308.05015) figures
- using the CI env var to trigger FakeThrust (thus making it easier to locally reproduce CI behaviour)
- renumbered figured in de Jong et al. breakup example to match final paper
- new tests (codecov now reports 80%!), code cleanups

- `RelaxedVelocity` dynamic (allowing for relaxation to terminal speeds) and relative fall velocity attribute refactor
- mermaid diagrams in `README` depicting PySDM submodule organisation and what's being passed where in the hello-world example

thanks to bradybhalla and edejong-caltech!

- PySDM-examples repo contents moved into PySDM repo (retaining separate PyPI packages)
- introducing test suites to shorten time-to-completion of CI runs
- switching from BDF to LSODA SciPy solver for condensation tests
- speeding up super-droplet count product
- using devops_tests in CI to share common test code across open-atmos projects
- more test cases added for test_n_breakups
- clarified literature references (incl. class dependency structure) in latent heat, diffusion kinetics and diffusion thermics formulae

thanks claresinger, abulenok and AgnieszkaMakulska for contributions, reviews and issue reports.

- updated multi-step breakup algorithm (kudos abulenok & edejong-caltech)