Resource Explorer not working with new AWS regions

This issue #3084 fixed that new regions can be connected to in resource explorer. However, when connecting to a new region (e.g. eu-central-2) some resources cannot be connected to and result in a [Unavailable in region] message.

## Steps to reproduce the issue

beware all new regions are opt-in and need to enabled first in your AWS account
2. Click on Resources in Resource Explorer
3. Add EC2::Host and/or EC2::VPC and click on it --> [Unavailable in region]

## Expected behavior
Either [No resources found] if no resources are deployed or a list of the deployed resources.

## System details (run the `AWS: About Toolkit` command)

- OS: Darwin arm64 21.6.0
- Visual Studio Code version: 1.75.1
- AWS Toolkit version: 1.62.0

Start by reproducing the issue in the AWS Toolkit Resource Explorer after enabling an opt-in region such as eu-central-2, then inspect how EC2::Host and EC2::VPC resources are handled. Verify the behavior against the expected outcome: show [No resources found] when empty or list deployed resources instead of [Unavailable in region].

Written by the indexing model from the issue text.