Verticals: Resolve source of truth

[sixhours]

The spreadsheet and the current API differ significantly. The source of truth should be the current spreadsheet, which either needs to be made into its own API or merged with the existing API. Related to #57556

[sixhours]

I compared the two lists with a spreadsheet diff and confirmed that all of the verticals listed in the spreadsheet are also listed in the current API.

Knowing this, I'll add a new column to the current API's source spreadsheet with priority information from the spreadsheet. Then we can look up verticals by priority rather than just ID.

[sixhours]

We're not going to add priorities at this time (see #57556 (comment)), but the current API contains all the values from the secondary verticals list in the given spreadsheet, so it's safe to use. Marking this as resolved.