Update indicators with NAN codes

[dshemetov]

This issue will track the production and the merging of the PRs that add bare bones NAN code support for individual indicators (enable deletions by tracking nan "val" entries and add codes for data ranges). Related work on the DB side here.

• cdc_covidnet Add NAN code support to CDC CovidNet #914 not deployed, not published
• change_hc Add NAN code support to changehc #898
• claims_hosp Add NAN code support to claims_hosp #902
• combo_cases_and_deaths Add NAN code support to Combo Indicator #944
• covid_act_now Add NAN code support to CAN #989
• doctor_visits Add NAN code support to doctors visits #990
• google_health
• google_symptoms Add NAN code support to Google Symptoms #993
• hhs_facilities Add NAN code support to HHS Facilities #1006
• hhs_hosp Add NAN code support to HHS Hosp #1008
• jhu Add NAN code support to JHU #839
• nchs_mortality Add NAN code support to NCHS Mortality #1016
• quidel Add NAN code support to Quidel #866
• quidel_covidtest Add NAN code support to Quidel Covidtest #999
• safegraph Add NAN code support to Safegraph #845 no longer supported
• safegraph_patterns Add NAN code support to Safegraph Patterns #859
• usafacts Add NAN code support to USAFacts #843

[dshemetov]

Only a partial fix there

[nmdefries]

@dshemetov Can we close this?

[dshemetov]

Still a bunch of indicator update PRs in the queue from almost 2 years ago. Might still be worth pushing them through at some point, though low priority.