Implement a servers.url selecting logic in uptime monitoring

[newgene]

The current logic in src/utils/monitor.py is to pick the first entry from the servers block of API metadata:

smartAPI/src/utils/monitor.py

Line 113 in 9d20791

self.api_server = api_doc['servers'][0]['url']

We should implement a more flexible logic to pick the "preferred" servers.url entry for the uptime monitoring.

We can use the same logic from the BTE project, documented here:

biothings/biothings_explorer#442

also summarized in:

NCATSTranslator/TranslatorEngineering#71 (comment)