[SYNPY-1910] Remove support for python 3.10

[andrewelamb]

Problem:

• Python 3.10 is no longer supported. The minimum supported Python version must change to 3.11. The supported range is now 3.11–3.14.
• The package configuration, the CI matrices, and the documentation all refer to Python 3.10 as the minimum version.
• The code imports Self from typing_extensions. Python 3.11 adds typing.Self, so this import is not necessary now.

Solution:

Package configuration

• setup.cfg: removed the Programming Language :: Python :: 3.10 classifier. Changed python_requires from >=3.10, <3.15 to >=3.11, <3.15.
• pyproject.toml: changed the black target-version from ['py39'] to ['py311']. The old value was already out of date.
• pylintrc: changed py-version from 3.10 to 3.11. Pylint does not run in pre-commit or CI, but earlier PRs that dropped Python 3.8 and 3.9 also changed this value.

CI (.github/workflows/build.yml)

• Removed 3.10 from the unit-tests and check-deploy matrices. The matrices are now ['3.11', '3.12', '3.13', '3.14'].
• Integration tests now run on Python 3.11 and 3.14 (oldest and newest). The "minimum" version is now 3.11 in:
  • The Check for Secret availability condition.
  • The Download Failed Tests from Previous Attempt condition.
  • The run-integration-tests condition.
  • The SYNAPSE_PROFILE selection for Ubuntu, Windows and macOS. The profile names (Test*MinimumPython) did not change.
• The deploy job now uses Python 3.11.
• Changed the dependency cache key from -v33 to -v34, so that CI does not use old caches.

Documentation

• README.md: the list of tested versions is now 3.11, 3.12, 3.13 and 3.14. Added: "Version 4.15.0 and later needs Python 3.11 or higher."
• CONTRIBUTING.md: the supported versions are now >=3.11 and <=3.14. The example versions in the instructions for adding and dropping a Python version are one version later.
• docs/tutorials/reticulate.md: the minimum Python version is now 3.11.

Code cleanup: typing.Self

• In 18 files in synapseclient/models/ (models, mixins and protocols), removed from typing_extensions import Self and added Self to the existing from typing import ... line.
• No typing_extensions imports are left in synapseclient/, synapseutils/ or tests/.

Test cleanup

• tests/unit/synapseutils/unit_test_synapseutils_describe.py: removed the if sys.version_info < (3, 7, 0): branch, which could never run, and the unused import sys.