TS-2582: add traffic_cop debugging mode

Replace custom traffic_cop option parsing with the standard libts
API. This has the side-effect of now requireing a double-dash for
long options.

Instead of a build-time option to enable traffic_cop debugging, add
a command line option that simply logs debug messages to standard
output. Add another command line option to enable the debug log
level.
TS-2058: add an integration test for SSL certificate loading

Add the test-multicert-loading integration test to verify that SSL
certificate loading does not delay the proxy coming up and serving
traffic.