Ansible: add 1.5.0 upgrade notes and complete the changelog

[stas-schaller]

Summary

Ansible integration: documentation only. This adds an "Upgrading to 1.5.0" section to the integration README and the Galaxy collection README, and it completes the 1.5.0 changelog for the four fix PRs that already merged.

1.5.0 is a minor release, but #1209, #1211, and #1212 change how existing tasks behave. The upgrade notes give each change as old behavior, new behavior, and what to change in a playbook. I checked the old values against git history and the new behavior against the merged code and tests. I did not run playbooks against a vault for this PR, so a reviewer should read the migration steps for accuracy.

Changes

Documentation

• Add an "Upgrading to 1.5.0" section to both READMEs. The section is identical in both files.
• Add the missing KSM-1562 changelog entry. (KSM-1562)
• Label the KSM-1559 and KSM-1560 changelog entries as breaking changes, as KSM-1561 already is. (KSM-1559, KSM-1560)
• Add the missing KSM-1559 lines: check mode deleted records before this release, an unknown option now fails the task, and the cache option is ignored. (KSM-1559)
• Add ticket IDs to the Security and Fix entries. (KSM-1559, KSM-1560)
• Add the keeper_create crash fix entry to the Galaxy README, where it was missing, and put KSM-845 in the same place in both files.

Testing

cd integration/keeper_secrets_manager_ansible && pytest

Breaking Changes

None. This PR changes documentation only. It describes the breaking changes that #1209, #1211, and #1212 already merged.

Related Issues

• Jira: REL-5255
• Related: Ansible: raise ansible-core minimum to 2.15.13 (KSM-1561) #1209 (KSM-1561), Ansible: enforce SDK floors in execution environments (KSM-1562) #1210 (KSM-1562), Ansible: make keeper_remove idempotent (KSM-1559) #1211 (KSM-1559), Ansible: honor check mode and harden secret handling (KSM-1560) #1212 (KSM-1560)