Backfill has_issues for vulnerability_reads with external issue tracker

What does this MR do and why?

This MR schedules backfilling of has_issues column in vulnerability_reads table for records where it's currently false and there exists a row in vulnerabilities_external_issue_links for the same vulnerability_id

Related to #442573 (closed)

Database review

Update query:

SQL

UPDATE
  vulnerability_reads
SET
  has_issues = true
FROM
  (SELECT "vulnerability_reads".* FROM "vulnerability_reads" INNER JOIN vulnerability_external_issue_links ON
          vulnerability_reads.vulnerability_id =
          vulnerability_external_issue_links.vulnerability_id WHERE "vulnerability_reads"."vulnerability_id" BETWEEN 107198712 AND 107198768 AND "vulnerability_reads"."vulnerability_id" < 107198768) as sub_query
WHERE
  vulnerability_reads.vulnerability_id = sub_query.vulnerability_id

Query plan: https://console.postgres.ai/gitlab/gitlab-production-tunnel-pg12/sessions/26865/commands/83677

Query plan and timings

 ModifyTable on public.vulnerability_reads  (cost=9.19..60.66 rows=0 width=0) (actual time=125.588..125.591 rows=0 loops=1)
   Buffers: shared hit=47 read=49 dirtied=17
   I/O Timings: read=121.905 write=0.000
   ->  Nested Loop  (cost=9.19..60.66 rows=1 width=19) (actual time=9.556..121.731 rows=1 loops=1)
         Buffers: shared hit=27 read=44 dirtied=16
         I/O Timings: read=119.827 write=0.000
         ->  Merge Join  (cost=8.62..57.08 rows=1 width=28) (actual time=9.521..121.693 rows=1 loops=1)
               Merge Cond: (vulnerability_reads_1.vulnerability_id = vulnerability_external_issue_links.vulnerability_id)
               Buffers: shared hit=22 read=44 dirtied=16
               I/O Timings: read=119.827 write=0.000
               ->  Index Scan using index_vulnerability_reads_on_vulnerability_id on public.vulnerability_reads vulnerability_reads_1  (cost=0.57..64.89 rows=57 width=14) (actual time=9.485..121.598 rows=56 loops=1)
                     Index Cond: ((vulnerability_reads_1.vulnerability_id >= 107198712) AND (vulnerability_reads_1.vulnerability_id <= 107198768) AND (vulnerability_reads_1.vulnerability_id < 107198768))
                     Buffers: shared hit=20 read=44 dirtied=16
                     I/O Timings: read=119.827 write=0.000
               ->  Index Scan using idx_vulnerability_ext_issue_links_on_vulne_id_and_ext_issue on public.vulnerability_external_issue_links  (cost=0.14..5.46 rows=55 width=14) (actual time=0.016..0.030 rows=48 loops=1)
                     Buffers: shared hit=2
                     I/O Timings: read=0.000 write=0.000
         ->  Index Scan using index_vulnerability_reads_on_vulnerability_id on public.vulnerability_reads  (cost=0.57..3.58 rows=1 width=14) (actual time=0.031..0.031 rows=1 loops=1)
               Index Cond: (vulnerability_reads.vulnerability_id = vulnerability_reads_1.vulnerability_id)
               Buffers: shared hit=5
               I/O Timings: read=0.000 write=0.000

Time: 134.263 ms
  - planning: 8.466 ms
  - execution: 125.797 ms
    - I/O read: 121.905 ms
    - I/O write: 0.000 ms

Shared buffers:
  - hits: 47 (~376.00 KiB) from the buffer pool
  - reads: 49 (~392.00 KiB) from the OS file cache, including disk I/O
  - dirtied: 17 (~136.00 KiB)
  - writes: 0

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