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

vendor/github.com/hashicorp/go-hclog/nulllogger.go

@@ -0,0 +1,45 @@
+package hclog
+
+import (
+	"log"
+	"io/ioutil"
+)
+
+// NewNullLogger instantiates a Logger for which all calls
+// will succeed without doing anything.
+// Useful for testing purposes.
+func NewNullLogger() Logger {
+	return &nullLogger{}
+}
+
+type nullLogger struct{}
+
+func (l *nullLogger) Trace(msg string, args ...interface{}) {}
+
+func (l *nullLogger) Debug(msg string, args ...interface{}) {}
+
+func (l *nullLogger) Info(msg string, args ...interface{}) {}
+
+func (l *nullLogger) Warn(msg string, args ...interface{}) {}
+
+func (l *nullLogger) Error(msg string, args ...interface{}) {}
+
+func (l *nullLogger) IsTrace() bool { return false }
+
+func (l *nullLogger) IsDebug() bool { return false }
+
+func (l *nullLogger) IsInfo() bool { return false }
+
+func (l *nullLogger) IsWarn() bool { return false }
+
+func (l *nullLogger) IsError() bool { return false }
+
+func (l *nullLogger) With(args ...interface{}) Logger { return l }
+
+func (l *nullLogger) Named(name string) Logger { return l }
+
+func (l *nullLogger) ResetNamed(name string) Logger { return l }
+
+func (l *nullLogger) StandardLogger(opts *StandardLoggerOptions) *log.Logger {
+	return log.New(ioutil.Discard, "", log.LstdFlags)
+}