ddtrace/tracer: include appsec status into startup logging

[Julio-Guerra]

As a result of the first installation of AppSec at Datadog, it would be better adding extra logs to cover some blind spots we have with:

-tags appsec	DD_APPSEC_ENABLED	Log message
false	false	Nothing
false	true	INFO: appsec: enabled by the configuration but has not been activated during the compilation: please add the go build tag appsec to your build options to enable it
false	parsing error	ERROR: appsec: error while checking if appsec is enabled: could not parse DD_APPSEC_ENABLED value truc as a boolean value
true	false	DEBUG: appsec: disabled by the configuration: set the environment variable DD_APPSEC_ENABLED to true to enable it
true	true	INFO: appsec: starting with default recommended security rules
true	parsing error	ERROR: appsec: could not start because of an unexpected error: could not parse DD_APPSEC_ENABLED value truce as a boolean value No security activities will be collected. Please contact support at https://docs.datadoghq.com/help/ for help.

[knusbaum]

Minor nit for testing.

In addition, I'm hoping we can include appsec in the startup log line:

dd-trace-go/ddtrace/tracer/log.go

Line 72 in 4cfcd67

func logStartup(t *tracer) {

Since appsec is integrated into the tracer, and this specific log line is used by support to gather basic configuration and status information about the tracer, it would be a good place for it.

If Appsec can export a simple Status() string function or something like that to report its status ("running", "disabled", etc.), we can use that to report appsec status along with the rest of the startup log stuff.