fix: adapt for v2, fix default privileges and add examples and tests

[fernandezcuesta]

Description of your changes

Adapt to Crossplane v2, fixes while testing it and add tests and examples on top of crossplane-contrib#313
Fixes crossplane-contrib#117

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable to ensure this PR is ready for review.

How has this code been tested

How has this code been tested

Locally with a kind cluster, running from the examples folder and verified with:

  SELECT                                                                                                                                                                                                                                 
      pg_get_userbyid(d.defaclrole) AS target_role,                                                                                                                                                                                        
      CASE d.defaclobjtype                                                                                                                                                                                                                 
          WHEN 'r' THEN 'table'                                                                                                                                                                                                            
          WHEN 'f' THEN 'function'                                                                                                                                                                                                         
          WHEN 'S' THEN 'sequence'                                                                                                                                                                                                         
          WHEN 'T' THEN 'type'
          WHEN 'n' THEN 'schema'
      END AS object_type,
      n.nspname AS schema,
      pg_get_userbyid((aclexplode(d.defaclacl)).grantee) AS grantee,
      (aclexplode(d.defaclacl)).privilege_type
  FROM pg_default_acl d
  LEFT JOIN pg_namespace n ON d.defaclnamespace = n.oid
  ORDER BY target_role, object_type, grantee;