add python 3.13 support

[emdneto]

Checklist for review

• Add the version in tox.ini
• Add the version in pyproject.toml trove classifiers
• Update github workflows accordingly with tox -e generate-workflows; lint and benchmarks use the latest supported version
• Update .pre-commit-config.yaml
• Update tox examples in the documentation

[emdneto]

Basically, tests at CI are failing for:

• opentelemetry-opencensus-shim 3.13 (Windows and Ubuntu)
• opentelemetry-exporter-opencensus 3.13 (Windows and Ubuntu)

opentracing-shim tests passes because we're not pinning grpcio in requirements, so it's installing a new version of grpcio, which supports python3.13.

If fixing the grpcio version in requirements tests passes