fix: mantle token mispriced (#4045)

## Explanation

Fixes an issue where prices were incorrect for Mantle, the native token
of chain 0x1388.

This happens because the symbol is `MNT`, but that's also the symbol of
Mongolia's fiat currency. CryptoCompare gives symbol preference to the
latter, and instead uses `MANTLE` to identify the crypto token:

-
https://data-api.cryptocompare.com/asset/v1/data/by/symbol?asset_symbol=MNT
-
https://data-api.cryptocompare.com/asset/v1/data/by/symbol?asset_symbol=MANTLE

I fixed this by adding an override mapping for tokens whose
CryptoCompare identifiers don't match their symbol, starting with `MNT`
-> `MANTLE`.

## References



## Changelog

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### `@metamask/assets-controllers`

- **FIXED**: Fixed price lookups for Mantle token

## Checklist

- [ ] I've updated the test suite for new or updated code as appropriate
- [ ] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [ ] I've highlighted breaking changes using the "BREAKING" category
above as appropriate

packages/assets-controllers/src/crypto-compare.test.ts

@@ -140,4 +140,13 @@ describe('CryptoCompare', () => {
       'Market does not exist for this coin pair',
     );
   });
+
+  it('should override native symbol when the CryptoCompare identifier is different', async () => {
+    nock(cryptoCompareHost)
+      .get('/data/price?fsym=MANTLE&tsyms=USD')
+      .reply(200, { USD: 123 });
+
+    const { conversionRate } = await fetchExchangeRate('USD', 'MNT');
+    expect(conversionRate).toBe(123);
+  });
 });

packages/assets-controllers/src/crypto-compare.ts

@@ -1,5 +1,11 @@
 import { handleFetch } from '@metamask/controller-utils';
 
+/**
+ * A map from native currency symbol to CryptoCompare identifier.
+ * This is only needed when the values don't match.
+ */
+const nativeSymbolOverrides = new Map([['MNT', 'MANTLE']]);
+
 /**
  * Get the CryptoCompare API URL for getting the conversion rate from the given native currency to
  * the given currency. Optionally, the conversion rate from the native currency to USD can also be
@@ -16,9 +22,11 @@ function getPricingURL(
   nativeCurrency: string,
   includeUSDRate?: boolean,
 ) {
+  nativeCurrency = nativeCurrency.toUpperCase();
+  const fsym = nativeSymbolOverrides.get(nativeCurrency) ?? nativeCurrency;
   return (
     `https://min-api.cryptocompare.com/data/price?fsym=` +
-    `${nativeCurrency.toUpperCase()}&tsyms=${currentCurrency.toUpperCase()}` +
+    `${fsym}&tsyms=${currentCurrency.toUpperCase()}` +
     `${includeUSDRate && currentCurrency.toUpperCase() !== 'USD' ? ',USD' : ''}`
   );
 }