fix: ignore 'type' field during late initialization for IAM user support

[fahedouch]

Description of your changes

Reproduction

1. Create a Cloud SQL IAM user with type: CLOUD_IAM_USER:

   apiVersion: sql.gcp.upbound.io/v1beta2
   kind: User
   metadata:
     name: test-iam-user
   spec:
     forProvider:
       instance: my-instance
       name: user@example.com
       type: CLOUD_IAM_USER

2. Wait for the resource to be created (Ready=True)

3. Check the type field in the manifest after a few reconciliation cycles

Current behavior: The type field becomes empty after reconciliation because the GCP API doesn't return it and LateInitializer resets it. This turns the IAM user into a BUILT_IN user.

Expected behavior: The type field should persist with the initially specified value CLOUD_IAM_USER.

How to Fix

Adds LateInitializer.IgnoredFields for the 'type' field in google_sql_user resource to prevent it from being reset to empty during reconciliation. The 'type' field is write-only and not returned by GCP API, causing IAM users (CLOUD_IAM_USER, CLOUD_IAM_SERVICE_ACCOUNT) to be incorrectly converted to BUILT_IN users.

Fixes #

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How has this code been tested