Genericize kubectl get operations

[jinnovation]

Relates to #69.

Currently, we define one function for getting all entities of a given resource type, for each of a finite set of resources, e.g. k8s-kubectl-get-{pods, nodes, ...}. All of these functions are identical save for the resource type that they retrieve.

As such, we generalize to a single implementation—k8s-kubectl-get—that accepts the resource type name and performs the get accordingly.

By extension, we rewire all call sites that assume the existence of per-type get functions to use the genericized counterpart—most notably the kubernetes-state-define-refreshers macro, which currently literally expects functions of those naming pattern to exist.

Similarly, we consolidate unit tests and, finally, remove the granular, per-type get functions.

[codecov-commenter]

Codecov Report

Merging #196 (7e3092d) into master (4290924) will decrease coverage by 0.66%.
The diff coverage is 21.42%.

@@            Coverage Diff             @@
##           master     #196      +/-   ##
==========================================
- Coverage   44.27%   43.60%   -0.67%     
==========================================
  Files          28       28              
  Lines        1554     1509      -45     
==========================================
- Hits          688      658      -30     
+ Misses        866      851      -15     

Impacted Files	Coverage Δ
kubernetes-commands.el	4.41% <0.00%> (ø)
kubernetes-configmaps.el	0.00% <0.00%> (ø)
kubernetes-deployments.el	0.00% <0.00%> (ø)
kubernetes-ingress.el	0.00% <0.00%> (ø)
kubernetes-jobs.el	19.35% <0.00%> (ø)
kubernetes-namespaces.el	0.00% <0.00%> (ø)
kubernetes-nodes.el	0.00% <0.00%> (ø)
kubernetes-pods.el	10.71% <0.00%> (ø)
kubernetes-secrets.el	0.00% <0.00%> (ø)
kubernetes-services.el	0.00% <0.00%> (ø)
... and 3 more

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[noorul]

LGTM, nice 💯