What
---
* Add target latency of 50ms for routing layer
* Write analysis done from https://gitlab.com/gitlab-org/gitlab/-/issues/432934

Why
---
We need to have a target of how much latency the cell router should add
to the request path, so make sure we don't affect our SLOs in an
negative way.

Reference: https://gitlab.com/gitlab-org/gitlab/-/issues/432934


Signed-off-by: Steve Xuereb <sxuereb@gitlab.com>