Backend image rendering as plugin (#11966)

* rendering: headless chrome progress

* renderer: minor change

* grpc: version hell

* updated grpc libs

* wip: minor progess

* rendering: new image rendering plugin is starting to work

* feat: now phantomjs works as well and updated alerting to use new rendering service

* refactor: renamed renderer package and service to rendering to make renderer name less confusing (rendering is internal service that handles the renderer plugin now)

* rendering: now render key is passed and render auth is working in plugin mode

* removed unneeded lines from gitignore

* rendering: now plugin mode supports waiting for all panels to complete rendering

* fix: LastSeenAt fix for render calls, was not set which causes a lot of updates to Last Seen at during rendering, this should fix sqlite db locked issues in seen in previous releases

* change: changed render tz url parameter to use proper timezone name as chrome does not handle UTC offset TZ values

* fix: another update to tz param generation

* renderer: added http mode to renderer service, new ini setting [rendering] server_url

pkg/plugins/datasource_plugin_test.go

@@ -1,35 +0,0 @@
-package plugins
-
-import (
-	"testing"
-)
-
-func TestComposeBinaryName(t *testing.T) {
-	tests := []struct {
-		name string
-		os   string
-		arch string
-
-		expectedPath string
-	}{
-		{
-			name:         "simple-json",
-			os:           "linux",
-			arch:         "amd64",
-			expectedPath: `simple-json_linux_amd64`,
-		},
-		{
-			name:         "simple-json",
-			os:           "windows",
-			arch:         "amd64",
-			expectedPath: `simple-json_windows_amd64.exe`,
-		},
-	}
-
-	for _, v := range tests {
-		have := composeBinaryName(v.name, v.os, v.arch)
-		if have != v.expectedPath {
-			t.Errorf("expected %s got %s", v.expectedPath, have)
-		}
-	}
-}