WIP: APISnoop Spyglass Lens

[hh]

This is an attempt at developing an APISnoop plugin to display coverage data within prow.k8s.io.
It's not yet ready for a full PR review against kubernetes/test-infra.

[hh]

I'm having a bit of trouble getting a our plugin to load:

~/test-infra/prow/cmd/deck$ ./runlocal 
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 14.4M    0 14.4M    0     0  4887k      0 --:--:--  0:00:03 --:--:-- 4887k
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 23209    0 23209    0     0  68869      0 --:--:-- --:--:-- --:--:-- 68869
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 2512k    0 2512k    0     0  1795k      0 --:--:--  0:00:01 --:--:-- 1795k
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  178k    0  178k    0     0   101k      0 --:--:--  0:00:01 --:--:--  101k
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    47  100    47    0     0    141      0 --:--:-- --:--:-- --:--:--   141
DEBUG: Rule 'com_google_protobuf' indicated that a canonical reproducible form can be obtained by modifying arguments shallow_since = "1551387314 -0800"
INFO: Analysed target //prow/cmd/deck:deck (2 packages loaded, 1561 targets configured).
INFO: Found 1 target...
Target //prow/cmd/deck:deck up-to-date:
  bazel-bin/prow/cmd/deck/linux_amd64_pure_stripped/deck
INFO: Elapsed time: 4.276s, Critical Path: 2.18s
INFO: 1 process: 1 linux-sandbox.
INFO: Build completed successfully, 2 total actions
INFO: Running command line: bazel-bin/prow/cmd/deck/linux_amd64_pure_stripped/deck '--pregenerated-data=/home/hippie/test-infra/prow/cmd/deck/localdata' '--static-files-location=./prow/cmd/deck/static' '--template-files-location=./prow/cmd/deck/template' '--spyglass-files-location=./prow/spyglass/lenses' --config-path /home/hippie/test-infra/prow/cmd/deck/../../config.yaml --INFO: Build completed successfully, 2 total actions
INFO[0000] Spyglass registered viewer buildlog with title Build Log. 
INFO[0000] Spyglass registered viewer junit with title JUnit. 
INFO[0000] Spyglass registered viewer metadata with title Metadata. 

Config updated here: 64df654#diff-406185368ba7839d1459d3d51424f104R39

deck:
  spyglass:
    size_limit: 500000000 # 500MB
    gcs_browser_prefix: https://gcsweb.k8s.io/gcs/
    testgrid_config: gs://k8s-testgrid/config
    testgrid_root: https://testgrid.k8s.io/
    viewers:
      "started.json|finished.json":
      - "metadata"
      "build-log.txt":
      - "buildlog"
      "artifacts/junit.*\\.xml":
      - "junit"
      "apisnoop.json":
      - "apisnoop"

[hh]

http://localhost:8080/view/gcs/kubernetes-jenkins/pr-logs/pull/72677/pull-kubernetes-bazel-test/1116397938919084033/

[hh]

It's just a simple copy of metadata, but now we can explore loading directly directly from prow jobs. @devaii @zachmandeville @heyste