Make error types more consistent

The way we define errors vary throughout the SDK. We sometimes define error types for specific calls, other times at the module level, and other times by pulling them in from elsewhere. While each approach can have its place, it doesn't appear to have been done with a lot of intent, and sometimes the Python module has differing error shapes from it's Rust counterpart. Many of our errors repeat themselves via thiserror (e.g. ExecutionError and executable::Error). We should have an agreed upon way we define errors that is consistent and intuitive across the SDK.

Start by surveying the Rust and Python error definitions, including thiserror uses such as ExecutionError and executable::Error, and compare the error shapes across both SDK counterparts. The issue does not name specific files or tests. Done means an agreed, documented approach is established and the duplicated or inconsistent error definitions are addressed consistently.