[Bug]: `primaryType` is not displayed on any of the `signTyped` signature screens

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**Describe the bug**
`primaryType` is not displayed on any of the `signTyped` signature screens. Instead, we see `Message` title on the signature header.
this issue is the same we had on Extension, see[ here](https://github.com/MetaMask/metamask-extension/issues/17076) for more context.

**Screenshots**


**To Reproduce**
_Steps to reproduce the behavior_
1. Go to `https://metamask.github.io/test-dapp/`
2. Click on Connect
3. Click on any of the Sign type data -- see no primaryType is displayed, and instead the header shows `Message`

**Expected behavior**
We should display the `primaryType` of the signature as the header, instead of `Message` text.
See how this was resolved on Extension [here](https://github.com/MetaMask/metamask-extension/pull/17077).

**Smartphone (please complete the following information):**

- Device: Samsung SM-A217F
- OS: Android 11.0
- App Version: v5.12.3 (1033)

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_to be added after bug submission by internal support / PM_
**Severity**

- How critical is the impact of this bug on a user?
- Add stats if available on % of customers impacted
- Is this visible to all users?
- Is this tech debt?

Start by reproducing the issue at the MetaMask test dapp with a sign-typed request, then trace the mobile signTyped signature screens that currently show `Message`. Done means the signature header displays the request's `primaryType` instead of `Message` on every signTyped screen.

Written by the indexing model from the issue text.