Add Ambassador Ingress controller as an addon

[concaf]

This PR adds Ambassador (https://www.getambassador.io/) as an addon to Minikube. Also, a tutorial has been added on how to use the same.

The motivation behind adding Ambassador as an addon is mostly around improving the UX around installing and configuring Ambassador. Ambassador is installed via our operator which makes sure than the Ambassador installation is healthy and up to date at all times.

CC: @brucehorn @inercia

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Can one of the admins verify this patch?

[medyagh]

@concaf this looks great ! thank you for adding this addon. do you mind sharing which driver and os did you try this on ?

have you tried it on the docker driver ?
I wonder if we need t open a port for it during container creation time for docker/podman drivers

[priyawadhwa]

Hey @concaf -- thanks for submitting this PR! Any update on medya's questions?

[codecov-commenter]

Codecov Report

Merging #8161 into master will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #8161      +/-   ##
==========================================
- Coverage   34.60%   34.59%   -0.02%     
==========================================
  Files         147      147              
  Lines        9378     9381       +3     
==========================================
  Hits         3245     3245              
- Misses       5736     5739       +3     
  Partials      397      397              

Impacted Files	Coverage Δ
cmd/minikube/cmd/node_start.go	9.37% <0.00%> (-0.63%)	⬇️
cmd/minikube/cmd/node_stop.go	13.33% <0.00%> (-0.96%)	⬇️

[concaf]

@medyagh @priyawadhwa sorry for the late reply!

do you mind sharing which driver and os did you try this on ?
have you tried it on the docker driver ?

I've tested this on the docker driver, on Fedora 30.

I wonder if we need t open a port for it during container creation time for docker/podman drivers

Nope, no such requirement. This pretty much requires the same stuff as the ingress addons.

(The force pushes are due to a rebase and updating the image, nothing major)

[priyawadhwa]

@concaf thanks! I think this change is big enough to warrant an integration test -- would you mind writing one?

The test would:

1. Start a minikube cluster, and enable the addon by adding the --addons=<addon name> flag (Sample code here)
2. Makes sure the installation was successful (as in, some expected pod came up as Running) (sample code here)
3. Try to configure Ambassador via an Ingress resource and make sure it works

You can add TestAmbassadorAddon to our addons_test.go file.

A lot of the code from TestAddons can be copied into TestAmbassadorAddon (I linked some key lines above).

Docs for quickly running an integration test locally can be found here. Please let me know if you have any questions!