fix: Allow empty result when looking for storage integration on refresh

[bneijt]

Trying to refresh the terraform state after deleting an integration, I get the error:
Error: Could not show storage integration: sql: no rows in result set

The issue seems to be that looking for a specific integration does deal with not finding that specific integration, triggering an error instead of allow the refresh flow to continue.

Steps to reproduce:

• Create a snowflake_storage_integration using the provider
• Delete the resulting integration
• Execute terraform refresh to update the state

Expected result:

• The provider should notice the resource gone and update the state
  Actual result:
• The provider errors out with the message: Error: Could not show storage integration: sql: no rows in result set

Terraform version: 1.0.7
Provider version: 0.25.19

I'm not a go developer, so this PR probably needs tests.

[bneijt]

Turns out you can nolonger terraform plan anything if the storage integration from your current state is missing, so I filed a bug to make it more visible to other users.

#696

[alldoami]

/ok-to-test sha=71d4885

[github-actions]

Integration tests success for 71d4885

[alldoami]

@bneijt could you fix the conflicts and I'll look at it again after? Sorry for the late review!

[alldoami]

/ok-to-test sha=d5a7131

[github-actions]

Integration tests success for d5a7131

[alldoami]

Thanks for working on this!