Fix the way replace_metadata drops event triggers (fix #5461)

[lexi-lambda]

Description

This PR fixes #5461 by changing the way replace_metadata updates event triggers. Instead of dropping and recreating them, HGE now performs a diff-and-patch against the existing metadata, which goes through the appropriate code paths to update the associated SQL functions and archive events.

Affected components

• Server

Related Issues

#5461

Server checklist

Metadata

Does this PR add a new Metadata feature?

• No

GraphQL

• No new GraphQL schema is generated

Breaking changes

• No Breaking changes

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[codingkarthik]

LGTM

[rakeshkky]

@lexi-lambda
With the metadata storage separation (#5797) the migration present in the PR becomes obsolete and event triggers are no longer stored in hdb_catalog.event_triggers. I'll take this up. Assigning myself.

cc @tirumaraiselvan

[tirumaraiselvan]

@rakeshkky This PR should be merged regardless because we need to cherry-pick it for v1.3.3

The new event trigger changes should happen on top of this.

[tirumaraiselvan]

test_server_upgrade is failing because circleci/postgres:11-alpine-postgis has a different FK constraint name:

postgres=# \d hdb_catalog.event_triggers;
          Table "hdb_catalog.event_triggers"
    Column     | Type | Collation | Nullable | Default 
---------------+------+-----------+----------+---------
 name          | text |           | not null | 
 type          | text |           | not null | 
 schema_name   | text |           | not null | 
 table_name    | text |           | not null | 
 configuration | json |           |          | 
 comment       | text |           |          | 
Indexes:
    "event_triggers_pkey" PRIMARY KEY, btree (name)
Foreign-key constraints:
    "event_triggers_schema_name_fkey" FOREIGN KEY (schema_name, table_name) REFERENCES hdb_catalog.hdb_table(table_schema, table_name) ON UPDATE CASCADE

[rakeshkky]

Server LGTM. However, these changes will become obsolete with metadata storage separation (see #5797).