Fix context handling for IR errors

[WillBAnders]

Currently, the context field for RhovasIr is never initialized for use in errors. I believe the primary issues here were with testing and library functions were unable to access the IR of their arguments, thus it never ended up being a priority. Therefore, this has two tasks:

• RhovasIr needs to have it's context field initialized, which should be used in errors for the analyzer/evaluator
• Standard library functions should have some method of accessing argument context and potentially the surrounding function

[WillBAnders]

This has a much wider scope than originally anticipated. Unlike the parser, semantic analysis errors should include context for things like variable declarations, assignments, and refined types. This requires a much more sophisticated approach to handling context than I had foreseen.

I think the next step with this is to build a mini-specification for what information should be included, and start with simple things like including the declaration for variables - anything before that is a bit too trivial and probably wouldn't justify the effort.

[WillBAnders]

First part for RhovasIr context was implemented in 12b58db; going to address the second part in this issue as well. Going to consider adding more context to the analyzer as a separate feature rather than part of this bug and will open a new issue for that.