[#18645] YSQL: Mitigate upgrade failure on yb_backend_xid add column.

Summary:
D26677 introduced the yb_backend_xid column to pg_stat_get_activity.
The corresponding migration script UPDATES the existing row for pg_stat_get_activity to add the new column.
This seemingly causes flakiness during upgrades owing to the fact that the system table update command does not update the local cat cache.
Subsequent to updation of the local cat cache, the views that are based on pg_stat_get_activity are recreated. During this process, the out of date cat cache throws an error that the new column is not found.
To mitigate this, this revision replaces the UPDATE with a DELETE + INSERT.

For long term tracking of the UPDATE issue please refer to GHI [[ #13500 | #13500 ]].

This revision also deletes a redundant operation wrt creating views in the same migration script.
Jira: DB-7569

Test Plan:
Jenkins: all tests

1. Run upgrade tests:
```
./yb_build.sh --java-test 'org.yb.pgsql.TestYsqlUpgrade'
```

2. Perform portal upgrades to latest master, as well as 2.19.X.

Reviewers: jason, tverona, fizaa, myang

Reviewed By: myang

Subscribers: yql, smishra

Differential Revision: https://phorge.dev.yugabyte.com/D27722

src/yb/yql/pgwrapper/ysql_migrations/V43__17087__yb_backend_xid_in_pg_stat_activity.sql

@@ -2,12 +2,24 @@ BEGIN;
   SET LOCAL yb_non_ddl_txn_for_sys_tables_allowed TO true;
 
   -- Add a column for distributed transaction ID in pg_stat_get_activity
-  UPDATE pg_catalog.pg_proc
-  SET proallargtypes = '{23,26,23,26,25,25,25,25,25,1184,1184,1184,1184,869,25,23,28,28,25,16,25,25,23,16,25,2950}',
-      proargmodes = '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
-      proargnames = '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,sslcompression,sslclientdn,yb_backend_xid}'
-  WHERE (proname = 'pg_stat_get_activity' AND
-      pronamespace = 'pg_catalog'::regnamespace);
+  -- TODO: As a workaround for GHI #13500, we perform a delete + insert instead
+  -- of an update into pg_proc. Restore to UPDATE once fixed.
+  DELETE FROM pg_catalog.pg_proc WHERE proname = 'pg_stat_get_activity' AND
+    proargtypes = '23' AND pronamespace = 'pg_catalog'::regnamespace;
+  INSERT INTO pg_catalog.pg_proc (
+    oid, proname, pronamespace, proowner, prolang, procost, prorows, provariadic, protransform,
+    prokind, prosecdef, proleakproof, proisstrict, proretset, provolatile, proparallel,
+    pronargs, pronargdefaults, prorettype, proargtypes, proallargtypes, proargmodes,
+    proargnames, proargdefaults, protrftypes, prosrc, probin, proconfig, proacl
+  ) VALUES (
+    2022, 'pg_stat_get_activity', 11, 10, 12, 1, 100, 0, '-', 'f', false, false, false, 
+    true, 's', 'r', 1, 0, 2249, '23', '{23,26,23,26,25,25,25,25,25,1184,1184,1184,1184,869,25,23,
+    28,28,25,16,25,25,23,16,25,2950}', '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+    '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,
+    query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,
+    backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,sslcompression,sslclientdn,
+    yb_backend_xid}', NULL, NULL, 'pg_stat_get_activity', NULL, NULL, NULL)
+  ON CONFLICT DO NOTHING;
 COMMIT;
 
 BEGIN;
@@ -42,50 +54,6 @@ BEGIN;
 
 COMMIT;
 
--- Update the pg_stat_activity view to include the distributed transaction ID
-DO $$
-BEGIN
-  IF NOT EXISTS (
-    SELECT TRUE FROM pg_attribute
-    WHERE attrelid = 'pg_catalog.pg_stat_activity'::regclass
-          AND attname = 'yb_backend_xid'
-          AND NOT attisdropped
-  ) THEN
-    CREATE OR REPLACE VIEW pg_catalog.pg_stat_activity
-    WITH (use_initdb_acl = true)
-    AS
-        SELECT
-            S.datid AS datid,
-            D.datname AS datname,
-            S.pid,
-            S.usesysid,
-            U.rolname AS usename,
-            S.application_name,
-            S.client_addr,
-            S.client_hostname,
-            S.client_port,
-            S.backend_start,
-            S.xact_start,
-            S.query_start,
-            S.state_change,
-            S.wait_event_type,
-            S.wait_event,
-            S.state,
-            S.backend_xid,
-            s.backend_xmin,
-            S.query,
-            S.backend_type,
-            yb_pg_stat_get_backend_catalog_version(B.beid) AS catalog_version,
-            yb_pg_stat_get_backend_allocated_mem_bytes(B.beid) AS allocated_mem_bytes,
-            yb_pg_stat_get_backend_rss_mem_bytes(B.beid) AS rss_mem_bytes,
-            S.yb_backend_xid
-        FROM pg_stat_get_activity(NULL) AS S
-            LEFT JOIN pg_database AS D ON (S.datid = D.oid)
-            LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid)
-            LEFT JOIN (pg_stat_get_backend_idset() beid CROSS JOIN
-                      pg_stat_get_backend_pid(beid) pid) B ON B.pid = S.pid;
-  END IF;
-
 -- Recreating system views that use pg_stat_get_activity to update their corresponding
 -- pg_rewrite entries.
 CREATE OR REPLACE VIEW pg_catalog.pg_stat_activity WITH (use_initdb_acl = true) AS
@@ -155,5 +123,3 @@ CREATE OR REPLACE VIEW pg_catalog.pg_stat_ssl WITH (use_initdb_acl = true) AS
         S.sslcompression AS compression,
         S.sslclientdn AS clientdn
     FROM pg_stat_get_activity(NULL) AS S;
-
-END $$;