fix(nocodb): Add postgres data source w/o CREATE ON DATABASE permission

[data-envoy]

Change Summary

This change adds a schemaExists check. The check doesn't need CREATE ON DATABASE permissions. Whereas the CREATE SCHEMA IF NOT EXISTS ?? AUTHORIZATION ?? does.

So it avoids throwing an error in case where both:

• The schema already exists
• The user doesn't have CREATE ON DATABASE permission

Fixes issue: #5398

Change type

• feat: (new feature for the user, not a new feature for build script)
• fix: (bug fix for the user, not a fix to a build script)
• docs: (changes to the documentation)
• style: (formatting, missing semi colons, etc; no production code change)
• refactor: (refactoring production code, eg. renaming a variable)
• test: (adding missing tests, refactoring tests; no production code change)
• chore: (updating grunt tasks etc; no production code change)

Test/ Verification

Running loaclly. Awaiting workflow