Stream device logs over the web_server /events Server-Sent Events feed so
'esphome logs' works on devices that have web_server: but no api:. This is
the logging counterpart to web_server OTA. Priority stays API, then MQTT,
then web_server. Reconnects automatically when the stream drops.
Factor the resolve-to-URLs step and the web_server port/auth lookup shared
with web_server OTA into a new web_server_helpers module (resolve_web_server_urls
and get_web_server_connection), with helpers.format_ip_url for IPv4/IPv6 URL
formatting, and broaden the missing-transport log error to suggest web_server:
alongside api:/MQTT/USB.
J. Nick Koston
a97f9e7cda