[v2] Add configuration to disable host prefix injection

[kdaily]

Issue #, if available:

Description of changes:

This change deviates from the upstream botocore to add the ability to disable jost prefix injection. It changes the default for inject_host_prefix in the Config object to be None (from True) so that the value can be determined using the configuration precedence. The fallback if the value remains True if it is set to None to preserve the CLI default behavior.

Testing

Tested with the following commands which uses an operation-specific host prefix:

1. Default case (no disable host prefix configuration set) results in the host prefix being added:

$ aws omics create-sequence-store --name "test-sequence-store1" --description "Test store" --endpoint-url https://localhost:1234/ --tags "Environment=Test"

Could not connect to the endpoint URL: "https://control-storage-localhost:1234/sequencestore"

2. Set config environment variable to False, which is the same as the default behavior:

AWS_DISABLE_HOST_PREFIX_INJECTION=False aws omics create-sequence-store --name "test-sequence-store1" --description "Test store" --endpoint-url https://localhost:1234/ --tags "Environment=Test"

Could not connect to the endpoint URL: "https://control-storage-localhost:1234/sequencestore"

3. Set config environment variable to True, which prevents the host prefix from being prepended to the endpoint URL:

$ AWS_DISABLE_HOST_PREFIX_INJECTION=True aws omics create-sequence-store --name "test-sequence-store1" --description "Test store" --endpoint-url https://localhost:1234/ --tags "Environment=Test"

Could not connect to the endpoint URL: "https://localhost:1234/sequencestore"

I also confirmed the behavior applies when using the configuration file setting disable_host_prefix_injection, and even when not using a custom endpoint URL.

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