fix: Add MANTLE support for conversion rates

[Prithpal-Sooriya]

Explanation

It seems that the MANTLE ERC20 tokens have wildly different USD/fiat conversions that what we had expected. This is amplified if you have more tokens.

Doing some digging, it seems that the balance/market data calculation is processed in the fetchAndMapExchangeRatesForUnsupportedNativeCurrency flow (for unsupported currencies).

Code Flow

Starts here...
Which calls this
Which is a renamed export of fetchExchangeRate which doesn't use that conversion

Inspecting extension network shows that we fetch the conversion rate using this URL:
https://min-api.cryptocompare.com/data/price?fsym=ETH&tsyms=MNT

This is incorrect as it is not using the correct symbol override. The url should be:
https://min-api.cryptocompare.com/data/price?fsym=ETH&tsyms=MANTLE

This gives a much better unsupported conversion number that what it currently is.

References

Changelog

@metamask/assets-controllers

• FIXED: update crypto-compare-service fetchExchangeRate to allow symbol overrides for mantle.

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
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes

[salimtb]

can you update and complete the PR description pls