Pipeline: Refactor cdc_wisqars to ingest new data

[benhammondmusic]

Description and Motivation

Adjusts cdc_wisqars data source to handle updated source data for gun homicides and gun suicides

• renames by race source files to match loading pattern
• uses existing WISQARS constants instead of strings
• revert to remove loading of general "gun_deaths" for now; will re-implement in future PR
• rename some variables for clarity
• move renaming of values and column names to their HET versions earlier in the code flow when possible
• handle loading of HISPANIC and UNKNOWN race rows from the ethnicity source data
• switch over tests to read in the real source data

Has this been tested? How?

• test source data and golden data updated and passing

Types of changes

(leave all that apply)

• Refactor / chore

New frontend preview link is below in the Netlify comment 😎

[eriwarr]

Looks great!