refactor: routes constants (#27078)

## **Description**

This is one small step in the larger task to refactor routing, in order
to speed up load time (MetaMask/MetaMask-planning#2898)

The changes are mostly to increase DRY, and to make a closer coupling
between connected routes and their analytics tracking names.

I wanted to get this in separately in order to reduce complexity and
merge conflicts later.

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## **Related issues**

Progresses: MetaMask/MetaMask-planning#2898

## **Manual testing steps**
## **Screenshots/Recordings**
### **Before**
### **After**
## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [ ] I’ve included tests if applicable
- [ ] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

Co-authored-by: legobeat <[email protected]>

Author: HowardBraham