Upgrade ICAP protocol parser

[yadij]

Use the new Parser model for message parsing based on HTTP/1 message format to perform initial parse of ICAP messages for OPTIONS response messages.

Add (some) missing 93,2 debug tracing for ICAP traffic.

Polished Http1::StatusLine to remove some hard-coded HTTP outputs and allow simpler more generic protocol label handling.

Add missing registration for ICAP as a protocol Squid can use.

[yadij]

FTR: code changes have not yet been runtime tested to verify accuracy of the resulting internal representation for OPTIONS response messages, nor debug display of parsed objects.

[yadij]

Marked as waiting for QA since ICAP testing still needed to see if there is any unexpected issues author and review cannot see. I will run it with c-icap echo service shortly, but third-party confirmation with a different service would be good.

[rousskov]

I removed S-waiting-for-QA because, I assume, you will merge this PR when it is approved regardless of whether somebody volunteers to perform more ICAP tests than you are willing to run. That label is meant to declare PRs blocked on testing. Please restore that label if the PR is indeed blocked on those ICAP tests.