Rework Cloud Foundry actuator support behind a pluggable abstraction

[philwebb]

We would like to change the /cloudfoundryapplication actuator support to a pluggable abstraction to allow more extensions in the future.

[philwebb]

Tasks:

• Work out what to do with WebFluxAdditionalHealthEndpointPathsConfiguration, JerseyAdditionalHealthEndpointPathsConfiguration, MvcAdditionalHealthEndpointPathsConfiguration
• See if we can remove @ConditionalOnAvailableEndpoint.considerEndpointExposers, currently used in MvcAdditionalHealthEndpointPathsConfiguration
• Determine if SbomEndpointAutoConfiguration not having EndpointExposure.CLOUD_FOUNDRY is intentional
• Deprecate EndpointExposure.CLOUD_FOUNDRY
• Add EndpointExposer to replace EndpointExposure.CLOUD_FOUNDRY
• Add value alias to @ConditionalOnAvailableEndpoint and migrate simple conditions

[wilkinsona]

I've opened #41890 for the SBOM endpoint's web extension on CF.

[philwebb]

"Add value alias to @ConditionalOnAvailableEndpoint and migrate simple conditions" should probably be a different issue as it's not really related.