Update Python support, documentation configuration and change linter to Ruff

• Make Python 3.11 the default image for CI
• Add support for Python 3.12
• Drop support for Python 3.9
• Bump dev version to Numpy 2.0 (no changes between 1.x and 2.0 observed)
• Bump ESA-PTR version to 1.4
• Bump Poetry min version to 1.8
• Bump pytest dependency to 8.x (for test group)
• Bump Sphinx version to 7.x (for docs)
• Bump Jupyterlab version to 4.x (for docs)
• Update ReadTheDocs configuration (for addons support)
• Change linter to ruff as replacement for flake8 and pylint.
• Reformat all the codebase with ruff check and ruff format (enforced in CI).
• Add explicit defusedxml (to avoid security issue (S314))
• Update License owner and copyright dates

⚠️ Possible breaking change

• Rename exceptions MissingKernel and MissingKernelsRemote as MissingKernelError and MissingKernelsRemoteError

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Fixes #89, #90 and #97 (closed).