Adds lambda_ephemeral_storage option for configuring the ephemeral storage.

[henryivesjones]

Adds a lambda_ephemeral_storage option to the chalice config file, which allows the user to configure the amount of ephemeral storage available to a lambda function. https://aws.amazon.com/blogs/aws/aws-lambda-now-supports-up-to-10-gb-ephemeral-storage/

I had to refactor the TypedAWSClient._update_function_config function to keep the complexity below 10.

Issue #, if available: 1962 https://github.com/aws/chalice/issues/1962 Description of changes: Adds a lambda_ephemeral_storage option to the chalice config file. Fixes broken links in docs.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[leobarcellos]

This is nice.