fix(custom-resources): support region for AwsCustomResource

[jogold]

Allow to specify region for AWS API calls in AwsCustomResource

Remove gitignored file lib/sdk-api-metadata.json.

Closes #4292

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[eladb]

I am not sure this is a good idea. What is the use case exactly? It's generally considered an anti-pattern to perform cross region operations. If users wish to invoke APIs in a region, they can just create a CFN stack in that region.

[konstantinj]

@eladb I'm trying to send messages to a shared sns topic in our main account. Idea is that all subaccounts can send there from all regions. We have several subscriptions in the main account in one region which is our central hub basically. Alternative would be to have from thios one region subscriptions to many sns topics in different region. But I guess that would be the exact same problem. I'm already querying other region endpoints in many of my lambda functions e.g. for peering connections I need this since I need to assume a role from another account to accept it. Actually I would like to do the peerings also in a custom resource so I can also accept the connections right away and be able to make connections to many other accounts/regions.

[konstantinj]

in #1796 @rix0rrr says "writing a Custom Resource to do a cross-region call". So I guess to be able to do this, this PR is needed.

[jogold]

@eladb I understand the request to be able to publish to a topic in another region and I can imagine use cases for this

Your call... if you don't want to support this I'll refactor this PR to only include the additional test on apiVersion.

[eladb]

I don't have dire objections... Maybe we can just add some warnings in the documentation of this property and explain to people that this can have implications on their blast radius...

Pull request has been modified.

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