fix: disable ALPN for non-HTTP routes

[guydc]

What type of PR is this?

What this PR does / why we need it:

• Adds an IR hint that can be used to distinguish between unspecified ALPN (empty list) and opt-out of ALPN
• By default, all non-HTTPS routes opt-out of ALPN
• If a client traffic policy defines ALPN protocols, non-HTTPS routes are opted-in

Which issue(s) this PR fixes:

Fixes #4456