…ture-flag-driven in PredictMarketDetails cp-7.69.0 (#27090)

## **Description**

The fee exemption logic in `PredictMarketDetails` was hardcoded to check
for a `'Middle East'` tag label, while `PredictController` and
`PolymarketProvider` already used a feature-flag-driven approach via
`feeCollection.waiveList`. This PR aligns the UI layer with the existing
pattern:

- **`parsePolymarketEvents`**: Switch tag mapping from `t.label` to
`t.slug` so parsed market tags match the slug-based `waiveList` entries
used by `waiveFees()`
- **`selectPredictFeeCollectionFlag`**: New selector that reads the
`predictFeeCollection` remote feature flag, falling back to
`DEFAULT_FEE_COLLECTION_FLAG`
- **`PredictMarketDetails`**: Replace hardcoded `tags?.includes('Middle
East')` with `tags?.some(slug => waiveList.includes(slug))` driven by
the selector
- Added defensive optional chaining on `tags` access for safety

## **Changelog**

CHANGELOG entry: null

## **Related issues**

Fixes:
[PRED-736](https://consensyssoftware.atlassian.net/browse/PRED-736)

## **Manual testing steps**

```gherkin
Feature: Fee exemption display on market details

  Scenario: user views a market with a tag in the waiveList
    Given the remote feature flag predictFeeCollection has waiveList containing 'middle-east'
    And a market has the tag slug 'middle-east'

    When user navigates to the market details screen
    Then the fee exemption message is displayed

  Scenario: user views a market without waived tags
    Given the remote feature flag predictFeeCollection has waiveList containing 'middle-east'
    And a market only has tag slugs 'sports' and 'politics'

    When user navigates to the market details screen
    Then the fee exemption message is not displayed

  Scenario: user views a market when waiveList is empty
    Given the remote feature flag predictFeeCollection has an empty waiveList
    And a market has any tags

    When user navigates to the market details screen
    Then the fee exemption message is not displayed
```

## **Screenshots/Recordings**

### **Before**

N/A — logic change only, no visual diff

### **After**

N/A — logic change only, no visual diff

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I've included tests if applicable
- [x] 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-mobile/blob/main/.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.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Changes Predict market `tags` from human-readable labels to slugs and
uses remote `predictFeeCollection.waiveList` to control fee-exemption
UI, which could affect any UI/analytics expecting label-form tags. Logic
is straightforward and covered by updated/additional selector and view
tests.
> 
> **Overview**
> Aligns fee-exemption behavior in `PredictMarketDetails` with the
fee-collection feature flag by replacing the hardcoded `'Middle East'`
tag check with a `waiveList` (slug) match from the new
`selectPredictFeeCollectionFlag` selector (defaulting to
`DEFAULT_FEE_COLLECTION_FLAG`).
> 
> Updates Polymarket parsing to store market `tags` as tag **slugs**
(`t.slug`) instead of labels, and adjusts tests to validate the new
slug-based exemption behavior plus selector fallbacks when the remote
flag is missing/null/undefined.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
daf0e58. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->