Refactor Header and SideNav for easier packaging as a static route

[AlanGreene]

Changes

https://github.com/tektoncd/dashboard/issues/2452

Refactor the Header and SideNav components so that they can be more easily consumed as part of a statically defined route using the new React Router data APIs. This means the header and logout button are no longer pure UI components, and are moved to the containers folder instead, so they can use Dashboard-specific APIs and data as needed. These components are quite specific to the Dashboard application anyway so didn't really make sense as pure UI components in the first place.

/kind misc

Submitter Checklist

As the author of this PR, please check off the items in this checklist:

• [ ] Docs included if any changes are user facing
• [ ] Tests included if any functionality added or changed
• [ ] Follows the commit message standard
• [ ] Meets the Tekton contributor standards (including functionality, content, code)
• [ ] Has a kind label. You can add one by adding a comment on this PR that contains /kind <type>. Valid types are bug, cleanup, design, documentation, feature, flake, misc, question, tep
• [ ] Release notes block below has been updated with any user facing changes (new features, significant UI changes, API changes, bug fixes, changes requiring upgrade notices or deprecation warnings)
• [ ] Release notes contains the string "action required" if the change requires additional action from users switching to the new release

Release Notes

NONE

[AlanGreene]

/test all

[tekton-robot]

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