test(plugin): improve test coverage for pprof (#7473)

Add tests for Startup/Shutdown methods and HTTP endpoints.
Enhance setup tests with edge cases. Increases test coverage
from 58% to 100%.

Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>

plugin/pprof/setup_test.go

@@ -29,6 +29,12 @@ func TestPProf(t *testing.T) {
 		{`pprof {
                    block 20 30
                 }`, true},
+		{`pprof {
+                   block invalid
+                }`, true},
+		{`pprof {
+                   unknown_property
+                }`, true},
 		{`pprof
           pprof`, true},
 	}