Remove promlens deployment

[paulfantom]

What is missing?

Promlens being separated into a helm chart.

Why do we need it?

To simplify testing and improve logical grouping. Ideally each component is shipped from some other helm chart and tobs should provide an opinionated way to join those components together.

Anything else we need to know?:

[paulfantom]

Decision was to remove promlens from the installation.

[paulfantom]

First step would be to not enable promlens by default, which is done in #398

Full removal will follow after 0.11.0 release.

[nhudson]

Will wait till #471 is complete before working through this.