[Feature]: Move to the shared CCPBioSim workflows #49

Problem or motivation

CI in this repository is maintained on its own. Its workflow files repeat setup steps and hardcode Python, OS and dependency versions. Every CI fix has to be made here as well as in the other CCPBioSim packages, so the repositories drift apart.

Proposed solution

Move to the latest release of the shared CCPBioSim workflows, using the same file layout as the other repositories in the organisation.

• pr.yaml runs Unit, Docs and Pre-commit, plus Conda build if the package has a conda recipe. Unit is one call to ci-test-python, or ci-test-conda for packages that need programs pip cannot install. Coverage is on, and lowest-dependencies-check: true reinstalls the lowest allowed dependencies and re-runs the tests in each leg.
• weekly-tests.yaml runs on Mondays with the lowest-dependencies check and replaces any existing scheduled test workflows.
• coveralls-main.yaml builds the coverage baseline on pushes to main.
• Remove workflows that the shared ones make redundant, such as separate dependency-floor or daily test workflows.
• Install Python dependencies from pyproject.toml, so the unit tests run at the newest version in range and the lowest-dependencies step runs at the oldest. Conda provides only the programs pip cannot install. Python versions come from the shared defaults unless requires-python is narrower, in which case the workflows set python-versions.
• Point the release and license-year workflows at the shared release-* and maintenance-license-year workflows. Existing secret names stay as they are.
• Add .github/renovate.json extending the shared renovate/default and renovate/python presets, if it isn't there already.
• Update the README badges.

Additional context

• The shared workflows and their inputs are described in the README of CCPBioSim/.github.
• Reference migrations: CodeEntropy (pip), aiida-amber and aiida-gromacs (conda).