fix(ramps-controller): skip payment methods fetch when token is unsupported by provider

[AxelGes]

Summary

• In setSelectedProvider, skip the getPaymentMethods fetch when the selected token is explicitly not supported by the new provider (based on supportedCryptoCurrencies)
• Previously, the fetch would proceed with an unsupported token's assetId, causing the API to return empty results — leaving the user with no payment methods and no feedback
• The UI's Token Not Available modal handles this case, so no fetch is needed

How it works

supportedCryptoCurrencies is treated as a blocklist hint: if the field is absent or doesn't explicitly exclude the token, we fetch as usual. Only skip when supportedCryptoCurrencies[assetId] is explicitly false.

Test plan

• Select a token, change provider to one that explicitly doesn't support the token — confirm payment methods are not fetched and Token Not Available modal appears
• Select a supported token, change provider — confirm payment methods load normally

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Note

Low Risk
Low risk: a small guard in setSelectedProvider to avoid an unnecessary getPaymentMethods call based on provider metadata, covered by targeted unit tests. Main risk is behavioral change if supportedCryptoCurrencies data is incomplete or incorrect.

Overview
Prevents setSelectedProvider from fetching payment methods when the currently selected token is explicitly unsupported by the newly selected provider (via provider.supportedCryptoCurrencies[assetId] === false), avoiding misleading empty payment-method state.

Adds unit tests for the new skip/fetch conditions (unsupported token, supported token, and missing supportedCryptoCurrencies field) and documents the fix in the ramps-controller changelog.

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