Support file-based health checks/probes

[leochr]

Support a configuration option for file-based health checks/probes

See #687 for more details

[leochr]

Meeting notes - September 15, 2025 (Leo, Kirby):

• Investigate the possibility of looking up the image manifest to determine the Liberty version from labels such as liberty.version. We'll have to deal with image access (pull secret, service account) if the image is in a secured registry.
• We should use the image's SHA value to avoid looking up the version if it's already known
• Knowing the Liberty version would be helpful for this file-based probe feature, only available in 25.0.0.6+ as well as the securityUtility/LTPA encryption change (25.0.0.2+), and possible others

[kabicin]

Below are the file-based health check support changes ready for review (without Liberty version checks):
OLO: #774
WLO: WASdev/websphere-liberty-operator#799
RCO: application-stacks/runtime-component-operator#725
Tests: https://github.ibm.com/websphere/operators/pull/258

[leochr]

Meeting Notes - October 25, 2025:

• Add an option to skip over Liberty version checks (for users that are running latest/recent Liberty)
• Any optimization to do on our side to avoid looking up the image manifest if the application image didn’t change?
• Update Liberty version packaged with Operator. Set flag to retain current LTPA behaviour (use current/older algorithm)
• Less priority: Enable mpHealth feature via the Operator (add config to configDropins/defaults to avoid overriding user config in server.xml). Check if Liberty supports feature config without version.