Change `vulnerability_reads` query to utilize denormalized columns

Why are we doing this work

After populating the data for the recently introduced traversal_ids and archived columns, we can adjust our read queries to improve the performance of the group-level vulnerability report page.

In this issue, we will remove the join to the projects table and use the archived column instead. Also, we will use the traversal_ids to reduce the amount of I/O.

Implementation plan

database Create the necessary indices
backend Adjust the queries to remove the projects table join and use traversal_ids instead of using namespace_id. If this is done correctly and the necessary indices introduced, the unnested_in_filters abstraction will rewrite the query and produce something similar to one below;

Example SQL

SELECT
    "vulnerability_reads".*
FROM
    "vulnerability_reads"
WHERE
    "vulnerability_reads"."vulnerability_id" IN (
        SELECT
            "vulnerability_reads"."vulnerability_id"
        FROM
            unnest('{1,4}'::smallint[]) AS "states" ("state"),
            unnest('{0,1,2,3,4}'::smallint[]) AS "report_types" ("report_type"),
            unnest('{4,5,6,7}'::smallint[]) AS "severities" ("severity"),
            LATERAL (
                SELECT
                    "vulnerability_reads"."state",
                    "vulnerability_reads"."report_type",
                    "vulnerability_reads"."severity",
                    "vulnerability_reads"."archived",
                    "vulnerability_reads"."traversal_ids",
                    "vulnerability_reads"."vulnerability_id"
                FROM
                    "vulnerability_reads"
                WHERE (traversal_ids >= '{9970}'
                    AND traversal_ids < '{9971}')
                AND "vulnerability_reads"."archived" = FALSE
                AND (vulnerability_reads."state" = "states"."state")
                AND (vulnerability_reads."report_type" = "report_types"."report_type")
                AND (vulnerability_reads."severity" = "severities"."severity")
            ORDER BY
                "vulnerability_reads"."severity" ASC,
                "vulnerability_reads"."traversal_ids" ASC,
                "vulnerability_reads"."vulnerability_id" ASC
            LIMIT 21) AS vulnerability_reads
    ORDER BY
        "vulnerability_reads"."severity" ASC,
        "vulnerability_reads"."traversal_ids" ASC,
        "vulnerability_reads"."vulnerability_id" ASC
    LIMIT 21)
ORDER BY
    "vulnerability_reads"."severity" ASC,
    "vulnerability_reads"."traversal_ids" ASC,
    "vulnerability_reads"."vulnerability_id" ASC
LIMIT 21

https://console.postgres.ai/gitlab/gitlab-production-tunnel-pg12/sessions/24662/commands/80146

Verification steps

Verify that the group-level vulnerability page is loading the vulnerabilities for gitlab-org group.