Jaeger preserves the trace data of router healthz endpoints
which is not so helpful for monitoring function metrics and
consumes storage to store such trace data.
This PR uses `GetStartOptions` to examine the request's path and
check if it's a request to healthz endpoint. If yes, skip and not
to trace it.
Encoded path means the URL path contains encoded string like "/foo%2Fbar".
Gorilla/Mux by default doesn't enable encoded path support, you need to enable
it when initializing the router.
This PR adds a new environment variable USE_ENCODED_PATH to the router
deployment to enable encoded path support.
This PR removes not so useful logs and changes most of Info level
log to Debug/Error level in hot path while preserving some of them
that is helpful for troubleshooting.
