Advanced search - allow queries for health in work item index

What does this MR do and why?

This MR adds support for GLQL health status query in Elasticsearch. Currently, health status holds the following 3 enum values: "on track", "at risk", and "needs attention". In both Postgres and ES, these values are saved as integer. So I am going to map them to their corresponding numeric values on Glql::WorkItemFinder level.

enum :health_status, {
  on_track: 1,
  needs_attention: 2,
  at_risk: 3
}

Below is the example mapping (GLQL field => Glql::WorkItemsFinder parameters => Search::Elastic::Filter parameter) of all possible variations for health field:

Specific Health Status Queries

GLQL Query	WorkItems Finder	ES Filter Name
health = "on track"	health_status_filter: "on_track"	health_status: 1
health != "on track"	not: {health_status_filter: ["on_track"]}	not_health_status: 1
health = "at risk"	health_status_filter: "at_risk"	health_status: 3
health = "needs attention"	health_status_filter: "needs_attention"	health_status: 2

Wildcard Health Status Queries

GLQL Query	WorkItems Finder	ES Filter Name
health = any	health_status_filter: "any"	any_health_status: true
health != any	health_status_filter: "none"	none_health_status: true
health = none	health_status_filter: "none"	none_health_status: true
health != none	health_status_filter: "any"	any_health_status: true

Combined Health Status Queries

GLQL Query	WorkItems Finder	ES Filter Name
health = "on track" and health != none	health_status_filter: "on_track"	health_status: 1
health != "on track" and health = any	not: {health_status_filter: ["on_track"]}, health_status_filter: "any"	not_health_status: 1, any_health_status: true

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Follow this guide to have ES enabled locally for GDK
2. GLQL relies on crypto.subtle, which is unavailable in insecure contexts (except for localhost), it won’t work if you're using a custom URL like http://gdk.test:3000 locally. To resolve this, one of the options is to enable HTTPS in GDK by following this link.
3. Enable the following feature flags in rails c:

=> Feature.enable(:glql_integration)
=> Feature.enable(:glql_work_items)
=> Feature.enable(:glql_es_integration)

4. Navigate to any issue comment or description field where Markdown is supported
5. Add the following GLQL query into the field:

```glql
display: table
fields: title, labels, health
query: group = "gitlab-org" and health = "on track"
```

6. Test with different health field variations provided above in the MR description section.

MR acceptance checklist

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Related to #540813 (closed)