[Healthcheck] Introduce the notion of Severity for checks

[rbayet]

The idea is to introduce the notion of severity for checks, going from lowest to highest :

• notice (that will be used in the future for functional checks, like "you have not declared any optimizers")
• minor / warning (for instance using extra primary shards when it's not needed)
• major / error (for instance when an Hÿva compatibility module is not installed)
• critical (replicas enabled when there is a single node in the Elasticsearch / OpenSearch Cluster)

The idea is to inject the severity in the constructor of the checks and passed on to the AbstractCheck class constructor where it will be store in a protected class variable.
If you want to rely on the existing \Magento\Framework\Notification\MessageInterface constants (SEVERITY_CRITICAL, SEVERITY_MAJOR, ...) which are int, the \Smile\ElasticsuiteCore\Api\Healthcheck\CheckInterface should then have two methods implemented in AbstractCheck :

• getSeverity
• getSeverityLabel (which will map the constant int to translated strings)

The severity label should be displayed in the grid after the status column when the check is in status "failed".
Keep the severity column empty for a check that is in status "passed".

The design of the labels should be similar to the status label but with the following color coding

• notice : yellow or light blue color scheme
• minor / warning : orange color scheme (sufficiently distinct from the notice if you're using yellow)
• major : similar to the actual "grid-severity-major" for the time being
• critical : similar to the actual "grid-severity-critical" for the time being

Feel free to hijack and contextualize those grid-severity-* pre-existing classes to the context of the healthcheck page (to avoid making side effects on other pages using those classes).

Also, please create two new classes named "grid-status-passed" and "grid-status-failed" for the status column (which is currently using grid-severity-major and grid-severity-notice)

• grid-status-passed: identical green color scheme to the current grid-severity-notice
• grid-status-failed: please re-use the white and black color scheme that we used for external indices on the indices list screen

Regards,

[rbayet]

Default injected severity for existing checks :

• GhostIndicesCheck : minor / warning
• HyvaCompatibilityCheck : major / error
• PackageVersionsMismatchCheck : critical
• PrimaryShardsConfigCheck : minor / warning
• ReplicasConfigCheck : critical