ci: azure now logs invalid SSH Key format

[blackboxsw]

correct integration-test failures seen on Azure Jammy.

Proposed Commit Message

Commit 50de985b refactored how invalid SSH key formats were treated by Azure.
They are still persisted to .ssh/authorized_keys with original invalid formatting,
now they log a diagnostic event to the Azure backplane for reporting.

Update the related integration test validating the debug logs emitted.

Additional Context

Commit 50de985 introducing overhaul of how SSH public-keys from IMDS are treated.

Test Steps

# setup .config/pycloudlib.toml with your [azure] creds.
CLOUD_INIT_PLATFORM=azure CLOUD_INIT_OS_IMAGE=jammy CLOUD_INIT_CLOUD_INIT_SOURCE=ppa:cloud-init-dev/daily tox -e integration-tests -- tests/integration_tests/bugs/test_lp1910835.py

Merge type

• Squash merge using "Proposed Commit Message"
• Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)