added safe cast for obs+lab result eval

[tuvaforrest]

Describe your changes

added a safe cast on the result column for labs and observations. For BP readings, the results column is being evaluated < <integer>, which throws an error if result is text, such as not given

How has this been tested?

Run in client env

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Checklist before requesting a review

• I have added at least one Github label to this PR (bug, enhancement, breaking change,...)
• My code follows style guidelines
• (New models) YAML files are categorized by sub folder and models listed in alphabetical order
• (New models) I have added a config to each new model to enable it for claims and/or clinical data
• (New models) I have added the variable tuva_last_run to the final output
• (Optional) I have recorded a Loom to explain this PR

Package release checklist

• I have updated dbt docs
• I have updated the version number in the dbt_project.yml

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