Chore: Rename 'primary' to 'pgsql' in the src-cli commands for database uploads

[marcleblanc2]

The pgsql / frontend database already has too much confusion over its name when TS teams work with self-hosted customer admins. As far as I'm aware, the src snapshot databases commands for taking and uploading database snapshots as part of the migration from self-hosted to our Cloud is the only place our customers see the same database get a bonus third name primary, adding unnecessary confusion to a process which is already a little overwhelming for our customers, specifically the types of customers we're encouraging to migrate from self-hosted to Cloud.

I propose renaming primary -> pgsql in these src-cli commands, because that's the name of the pod / container which our self-hosted customer admins and TS teams already work with on a day-to-day basis, and it matches the database's name in the SG Cloud infra, and the rest of the commands throughout the migration process:

Customer commands:

# pgsql / frontend database is the only one that doesn't match from container name to snapshot name
docker exec -i pgsql sh -c 'PGPASSWORD=sg pg_dump ... --username=sg --dbname=sg' > src-snapshot/primary.sql

# codeintel and codeinsights get a snapshot name which match the container names
docker exec -i codeintel-db sh -c 'PGPASSWORD=sg pg_dump ... --username=sg --dbname=sg' > src-snapshot/codeintel.sql
docker exec -i codeinsights-db sh -c 'PGPASSWORD=password pg_dump ... --username=postgres --dbname=postgres' > src-snapshot/codeinsights.sql

IE commands:

DROP DATABASE IF EXISTS "pgsql";
CREATE DATABASE "pgsql";

gcloud sql import sql $CLOUD_SQL_INSTANCE  \
  gs://$BUCKET/primary.sql  \ # Confusing primary.sql
  --database=pgsql            # Database is named pgsql inside our Cloud instances

This database is referred to as frontend in database schema code, however, our self-hosted customer admins are never exposed to the database name frontend; it is the pgsql container that they work with / are taking the snapshot out of. The database name inside the container is also sg, but renaming the src-cli commands to sg wouldn't be any clearer.

Test plan

Naming change

[bobheadxi]

It's been a long time since I've been here, but are there any other process docs we need to update that may reference this DB by its old name?