📖 testing: add jq variant for inspecting json logs

[chrischdi]

What this PR does / why we need it:

Documents a variant of using jq to inspect the json logs of tests.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

[fabriziopandini]

nice, thanks for documenting this!
/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 7659b10ef75dd80ccff0c1c0892eeaad0b95ba24

[killianmuldoon]

Awesome - thanks for adding this!

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: killianmuldoon

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[killianmuldoon]

/cherry-pick release-1.4

[k8s-infra-cherrypick-robot]

@killianmuldoon: once the present PR merges, I will cherry-pick it on top of release-1.4 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.4

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[k8s-infra-cherrypick-robot]

@killianmuldoon: new pull request created: #8633

In response to this:

/cherry-pick release-1.4

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[sbueringer]

Thank you!

[killianmuldoon]

/area documentation