Fix up Tutorials landing page and Tutorials left nav.

[steveperry-53]

Closes #8247.

This PR moves some tutorial files to different directories, so that the left nav includes all tutorials. This PR also aligns the Tutorials landing page with the Tutorials left nav.

Preview: https://deploy-preview-8557--kubernetes-io-master-staging.netlify.com/docs/tutorials/

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Deploy preview for kubernetes-io-master-staging ready!

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[steveperry-53]

/assign @Bradamant3

[Bradamant3]

this is beautiful

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Bradamant3

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[steveperry-53]

/lgtm

[k8s-ci-robot]

@steveperry-53: you cannot LGTM your own PR.

In response to this:

/lgtm

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[steveperry-53]

@Bradamant3, The bot ate your LGTM. Could you do it again? Thanks.

[Bradamant3]

/lgtm

[Bradamant3]

silly bot