Add Visualization API endpoint

[ajchili]

This change is 

[ajchili]

After investigating the current visualization components, I noticed that input paths are provided as a pattern rather than an array of strings as seen here and here. I believe it may be best to change the inputPaths parameter in the protobuf file to take in a single string to duplicate current behavior rather than an array of strings.

[IronPan]

would the ID be used? If not maybe it can be removed?

[ajchili]

For predefined visualizations it may not be necessary. However, for custom visualizations we will need a way to differentiate them if we only have a single enum type to denote custom visualizations.

[ajchili]

/hold
Determining the best course of action for python kernel spawning latency.

[ajchili]

/hold cancel
Determined best course of action for python kernel spawning latency. The go backend will manage a python kernel. This will remove the startup latency (roughly 6 seconds) involved with spawning a kernel per visualization.

[IronPan]

/lgtm
/approve

[k8s-ci-robot]

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