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/prometheus/common/expfmt/text_parse.go

@@ -556,8 +556,8 @@ func (p *TextParser) readTokenUntilWhitespace() {
 // byte considered is the byte already read (now in p.currentByte).  The first
 // newline byte encountered is still copied into p.currentByte, but not into
 // p.currentToken. If recognizeEscapeSequence is true, two escape sequences are
-// recognized: '\\' tranlates into '\', and '\n' into a line-feed character. All
-// other escape sequences are invalid and cause an error.
+// recognized: '\\' translates into '\', and '\n' into a line-feed character.
+// All other escape sequences are invalid and cause an error.
 func (p *TextParser) readTokenUntilNewline(recognizeEscapeSequence bool) {
 	p.currentToken.Reset()
 	escaped := false