Add route switching and proxy handling

[lucferbux]

Closes https://issues.redhat.com/browse/RHOAIENG-5141

Description

Update the service proxy to handle multiple model registries in a namespace.

Bring the model registry selector to the top.

Refactor the model registry selector context.

How Has This Been Tested?

Deploy the PR in the cluster with quay.io/repository/opendatahub/odh-dashboard:pr-2747

1. Go to the Model Registry section
2. Switch between Model Registries
3. Check how it's fetching the right routes

Test Impact

Request review criteria:

Self checklist (all need to be checked):

• The developer has manually tested the changes and verified that the changes work
• Commits have been squashed into descriptive, self-contained units of work (e.g. 'WIP' and 'Implements feedback' style messages have been removed)
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has added tests or explained why testing cannot be added (unit or cypress tests for related changes)

If you have UI changes:

• Included any necessary screenshots or gifs if it was a UI change.
• Included tags to the UX team if it was a UI/UX change (find relevant UX in the SMEs section).

After the PR is posted & before it merges:

• The developer has tested their solution on a cluster by using the image produced by the PR to main

[lucferbux]

/hold

[lucferbux]

@yih-wang This is the progress and change of layout with the Model Registry switcher.

[yih-wang]

@lucferbux That looks good. Thanks for all the efforts here!

[dpanshug]

looks good, just a small change

[mturley]

LGTM, I have one non-blocking question though.

[lucferbux]

/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lucferbux, mturley

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