Let code Files be evaluated in tool configured env

Although `code` tag is deprecated, the idea, I think, is great. If we can let `code` files be evaluated by tool configured env, not Galaxy system python, there could be a lot more use cases.

The issue names no files, tests, or entry points. Start by locating how deprecated code files are evaluated and how tool-configured environments are selected. Done would mean code files run in the configured tool environment instead of Galaxy's system Python, but the required scope is not defined.

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