Add Sidecar Status to tkn taskrun describe

[danielhelfand]

Closes #655

This pull request adds sidecar status information to tkn taskrun decribe. It also makes use of sidecar features added to test builder for pipeline v0.11.0-rc.

As of now, I do am not sure if there is a particular sorting pattern that makes sense for sidecars so I have decided to not sort the statuses in any way at this point.

Submitter Checklist

• Includes tests (if functionality changed/added)
• Run the code checkers with make check
• Regenerate the manpages, docs and go formatting with make generated
• Commit messages follow commit message best practices

Release Notes

Add sidecar status to tkn taskrun describe 

[tekton-robot]

The following is the coverage report on pkg/.
Say /test pull-tekton-cli-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/validate/validate.go	96.2%	97.0%	0.8

[vdemeester]

/lgtm

[tekton-robot]

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