legacy api methods not documented and potentially broken

[aagbsn]

while migrating the private api methods #807 I'm discovering some endpoints that aren't documented (e.g. no API docs) or don't work

curl -X GET "https://api.ooni.org/api/_/website_stats?probe_cc=hr&probe_asn=5391&input=google.com"
{"error":"Code: 209. (data1.htz-fsn.prod.ooni.nu:9000)"}

curl -X GET "https://api.ooni.org/api/_/test_coverage?probe_cc=HR" -H  "accept: application/json"
{ "error": "Code: 209. (data1.htz-fsn.prod.ooni.nu:9000)"}