Rename NB_API_QUERY_URL to NB_API_URL or similar

[alyssadai]

NB_API_QUERY_URL can be slightly confusing because it:

1. Does not refer to the query tool URL
2. Does not refer only to the /query endpoint for the API, rather it is the base URL for the API which endpoints are appended to

To improve clarity and prevent confusion with NB_QUERY_APP_BASE_PATH, maybe we can consider renaming this to simply NB_API_URL or NB_FAPI_URL.

[github-actions]

We want to keep our issues up to date and active. This issue hasn't seen any activity in the last 75 days.
We have applied the _flag:stale label to indicate that this issue should be reviewed again.
When you review, please reread the spec and then apply one of these three options:

• prioritize: apply the flag:schedule label to suggest moving this issue into the backlog now
• close: if the issue is no longer relevant, explain why (give others a chance to reply) and then close.
• archive: sometimes an issue has important information or ideas but we won't work on it soon. In this case
  apply the someday label to show that this won't be prioritized. The stalebot will ignore issues with this
  label in the future. Use sparingly!