* Rendering: base metrics

* Rendering: rendering_queue_size metric

* Chore: fix linter error

* Rendering metrics: refactoring

* Apply suggestions from code review

Co-Authored-By: Marcus Efraimsson <marcus.efraimsson@gmail.com>

* Rendering metrics: handle DeadlineExceeded errors

* Rendering metrics: don't measure canceled request time

* Rendering metrics: revert deleting summary for canceled requests

* Update pkg/services/rendering/rendering.go

Co-Authored-By: Marcus Efraimsson <marcus.efraimsson@gmail.com>

* Rendering: return ErrTimeout if context deadline exceeded

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>