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/aws/aws-sdk-go/internal/sdkio/io_go1.6.go

@@ -0,0 +1,10 @@
+// +build !go1.7
+
+package sdkio
+
+// Copy of Go 1.7 io package's Seeker constants.
+const (
+	SeekStart   = 0 // seek relative to the origin of the file
+	SeekCurrent = 1 // seek relative to the current offset
+	SeekEnd     = 2 // seek relative to the end
+)

vendor/github.com/aws/aws-sdk-go/internal/sdkio/io_go1.7.go

@@ -0,0 +1,12 @@
+// +build go1.7
+
+package sdkio
+
+import "io"
+
+// Alias for Go 1.7 io package Seeker constants
+const (
+	SeekStart   = io.SeekStart   // seek relative to the origin of the file
+	SeekCurrent = io.SeekCurrent // seek relative to the current offset
+	SeekEnd     = io.SeekEnd     // seek relative to the end
+)

vendor/github.com/aws/aws-sdk-go/internal/sdkrand/locked_source.go

@@ -0,0 +1,29 @@
+package sdkrand
+
+import (
+	"math/rand"
+	"sync"
+	"time"
+)
+
+// lockedSource is a thread-safe implementation of rand.Source
+type lockedSource struct {
+	lk  sync.Mutex
+	src rand.Source
+}
+
+func (r *lockedSource) Int63() (n int64) {
+	r.lk.Lock()
+	n = r.src.Int63()
+	r.lk.Unlock()
+	return
+}
+
+func (r *lockedSource) Seed(seed int64) {
+	r.lk.Lock()
+	r.src.Seed(seed)
+	r.lk.Unlock()
+}
+
+// SeededRand is a new RNG using a thread safe implementation of rand.Source
+var SeededRand = rand.New(&lockedSource{src: rand.NewSource(time.Now().UnixNano())})