Upgrade to Python 3.13 and install Python 3.13 in ClusterFuzzLite

[Adarshkumar0509]

Fixes #2105

Changes

• Updated Dockerfile base image from python:3.12.12-alpine3.22 to python:3.13.11-alpine3.22 with the SHA digest pinned correctly in the format image@sha256:...
• Updated .clusterfuzzlite/Dockerfile to explicitly install Python 3.13 via deadsnakes PPA as you suggested, since gcr.io/oss-fuzz-base/base-builder-python:ubuntu-25-04 base image is not yet available
• Updated pip and package installations in ClusterFuzzLite to use python3.13 explicitly

Testing

• Verified the Dockerfile has the correct SHA pin format
• ClusterFuzzLite Dockerfile now installs Python 3.13 via deadsnakes PPA on top of the ubuntu-24-04 base image

Notes

• All commits are GPG signed and verified
• Will update to Ubuntu 25.04 base image once gcr.io/oss-fuzz-base/base-builder-python:ubuntu-25-04 becomes available

[Adarshkumar0509]

Hii @sydseter All 12 checks are passing now. Python 3.13 is installed from source in the ClusterFuzzLite Dockerfile since the deadsnakes PPA is not available in the OSS-Fuzz base image. Please review when you get a chance. Thank you!

[Adarshkumar0509]

hii @sydseter , All ClusterFuzzLite checks are passing successfully. The only failing check is build-test-copi which is a pre-existing coverage issue in master (74.3% vs 80% minimum) and is unrelated to my Dockerfile changes. Before updating the branch, all 12 checks were passing. Please review when you get a chance. Thank you!