Add the ability to specify ExternalId and Tags in the boto3_options of TupleS3StoreBackend

[rosspb3]

Is your feature request related to a problem? Please describe.

A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
Inability to run Great Expectation with a TupleS3StoreBackend in a cross-account scenario where the role assumed has an AWS policy that restricts role access by ExternalId and Tags.

Describe the solution you'd like
The ability to specify an ExternalId and Tags when the role is assumed.

Describe alternatives you've considered
A less restrictive policy for assuming the role, or running Great Expectation within the same account. However, corporate security makes those changes difficult.