[PAY-3648] Migrate buy-usdc to sdk

[dharit-tan]

Description

Tried to convert to sdk functions just based on types.

Not sure about error-handling scheme for solanaRelay? Old world uses {res, error, errorCode} and most of our fns expect that.

How Has This Been Tested?

Finding it difficult to test these flows in Thailand even with VPN

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: d07caca403f09aff1e43d4f3bffcf273c99450d0

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[rickyrombo]

Can we close this?