Release v0.7.0

[V2arK]

Bumps setup.py to 0.7.0 so a GitHub Release on this commit publishes the
version its tag claims. publish.yml builds from whatever setup.py says, so
the two have to agree before the release is published.

Minor rather than patch: #152 adds a public fetch_logs(), makes four existing
public surfaces emit a DeprecationWarning, and adds typing-extensions as a
runtime dependency. None of that is a bug fix, and a caller running with
-W error or pytest's filterwarnings = error would have a patch upgrade break
their build. Nothing is removed — get_deployment_logs,
get_deployment_logs_range, deployment_log_session and DeploymentLogSession
all keep working.

Also adds a MANIFEST.in so requirements.txt reaches the source distribution.
setup.py reads that file to build install_requires, and setuptools does not
ship it by default, so pip install from the tarball has failed on
FileNotFoundError in every release so far. Wheels carry their dependency list
in their own metadata and pip prefers them, so the failure only surfaces when a
source build is forced. Riding along with the version bump follows what the
v0.6.0 release commit did with find_packages(exclude=...).

Test plan

./.venv/bin/python -m pytest tests/ -q                       # 119 passed
python -m pylint --rcfile ./scripts/pylintrc ./centml ./tests  # 10.00/10
python -m build --sdist --wheel                              # both built from this branch

The built sdist installed into a clean virtualenv, which is what fails on 0.6.0:

Check	0.6.0 (from PyPI)	this branch
pip install <wheel>	works	works
pip install <sdist>	FileNotFoundError: 'requirements.txt'	installs
requirements.txt in sdist	absent	present
import centml, centml --version	—	both work from the sdist install
resolved requirements	—	all ten, including typing-extensions