AWS::SecurityHub::Insight

## 1. Title
### AWS::SecurityHub::Insight

## 2. Scope of request
This issue is to add the ability to manage SecurityHub Custom Insights. This includes [creating new insights](https://boto3.amazonaws.com/v1/documentation/api/1.10.45/reference/services/securityhub.html#SecurityHub.Client.create_insight), [updating existing insights](https://boto3.amazonaws.com/v1/documentation/api/1.10.45/reference/services/securityhub.html#SecurityHub.Client.update_insight), and [removing existing insights](https://boto3.amazonaws.com/v1/documentation/api/1.10.45/reference/services/securityhub.html#SecurityHub.Client.delete_insight).

## 3. Expected behavior
Normal CFN resource behaviour.

## 4. Suggest specific test cases
Normal CFN resource test cases.

## 5. Helpful Links to speed up research and evaluation
* AWS CLI: https://docs.aws.amazon.com/cli/latest/reference/securityhub/index.html
* Boto3 API: https://boto3.amazonaws.com/v1/documentation/api/1.10.45/reference/services/securityhub.html

## 6. Category (required) - Will help with tagging and be easier to find by other users to +1
Security (IAM, KMS...)

## 7. Any additional context (optional)

Start with the linked AWS CLI and Boto3 SecurityHub API references, focusing on create_insight, update_insight, and delete_insight. Done means CloudFormation can manage SecurityHub custom insights with normal resource behavior and the suggested resource test cases pass.

Written by the indexing model from the issue text.