Autocomplete: do not report some network errors to Sentry

[valerybugakov]

Context

• This PR makes our error reporting rules more strict on top of Autocomplete: do not report auth errors to Sentry #1028 by omitting network errors with a network status >= 500. The assumption is that these errors are already monitored on the backend.
• Filtering logic is moved right into the Sentry's beforeSend hook to ensure we do not accidentally report these types of errors from another captureException call site.
• A separate NetworkError class is added in addition to the TracedError to distinguish between transport-level and application logic errors.
• Disabled Sentry error reporting for non-production environments + introduced an environment variable to enable it for local debugging.
• Addresses the third most reported Sentry error read ECONNRESET (292k events). It should help us to keep the volume of reported errors under control.

Test plan

Tested locally.

[dominiccooney]

Looks good, but again we don't need to touch proto, the constructor already does that.