[connectors/http] prevent errors caused by multi-byte characters in paths

[spalger]

Since nodejs/node@b961d9fd83, http.request() will throw an error if multi-byte characters are used in the URL path, which is not currently being caught and passed back to the callback.

This may be true in a lot of places, but such is the nature of callbacks.

[LeeDr]

@spalger does this PR fix it just so Kibana doesn't crash on multi-byte chars but it still fails?
Or does this fix it so we can successfully use multi-byte chars in index pattern names?

[spalger]

@LeeDr this does not allow us to use multi-byte chars in Kibana, but it will properly forward the errors to the callback rather than crashing the process. See elastic/kibana#29210 for the other part of the solution.

[spalger]

Ran the unit tests locally ✅