[SYS] Better handling of certs and OTA checks (#1695)

Add a macro to enable removal of update checks
Separate certificates from user_config.h
Consider latest version as the default
Do not use a cert if the url is not
Simplify AWS macro scope

main/certs/default_client_key.h

@@ -0,0 +1,5 @@
+const char* ss_client_key PROGMEM = R"EOF("
+-----BEGIN RSA PRIVATE KEY-----
+...
+-----END RSA PRIVATE KEY-----
+")EOF";