Add "total exposure" notice to stream permissions

[jeffsmale90]

Description

The "stream" permissions are very complex, and it's difficult to determine the total amount that a given permission exposes to the recipient.

This PR updates erc20-token-stream and native-token-stream permissions to add a "total exposure" notice. This will show as a field similar to "Amount per second".

• "Amount per second" and "Total exposure" have been rerendered as text fields instead of disabled input fields.
• Updates test for "no expiry" notice.

Minor refresh of uneditable fields:

• Display with label above the value, identical to "Stream rate" and "Total exposure"
• Will not be rendered if they don't have a value (previously rendered with just a label and no context about why there's no value)

Note: no "Max amount"

Manual testing steps

• Request an erc20-token-stream or native-token-stream permission
• If an expiry or max-amount is specified, expect "This permission grants a total of amount token"
• if neither expiry or max-amount is specified, expect "This permission grants an unlimited amount"

Add / remove expiry and max amount and adjust the token amounts to validate different outcomes.

Screenshots/Recordings

Pre-merge author checklist

• I've followed MetaMask 7715 Permissions Snaps Contributor Docs and MetaMask 7715 Permissions Snaps Coding Standards.
• 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 format if applicable

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.

---

Note

Medium Risk
Adds new exposure calculation and surfaces it in the confirmation UI for stream permissions; incorrect math/formatting could misrepresent a permission’s effective limits to users.

Overview
Adds a “Total exposure” display to erc20-token-stream and native-token-stream confirmation screens, derived from max amount and/or stream duration (expiry) and shown as Unlimited when uncapped.

Introduces deriveExposureForStreamingPermission in permissions/rules.ts, threads totalExposure through stream deriveMetadata/metadata types, and updates stream rate rendering to use display-style Field components instead of disabled inputs.

Refreshes uneditable field rendering across InputField, DateTimePickerField, DropdownField, TextField, and Field (vertical layout + hide empty uneditable values), updates English copy from expiry to expiration date, and adjusts snapshots/tests accordingly.

^{Written by Cursor Bugbot for commit 32981b3. This will update automatically on new commits. Configure here.}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, have a team admin enable autofix in the Cursor dashboard.}

[mj-kiwi]

LGTM