[Spike] Refactor precision amounts

[twblack88]

While in the process of refactoring things in RFOX land and deciding to whether or not I should store precision as its own field or keep on deriving in-place, there's something I remembered coming across a few times in Uniswap SDK and finally found back... very close to the infamous amounts package that never came to be (IYKYK)

https://github.com/Uniswap/sdks/blob/9cd39edd4771a3817a05c417d1da3610790d4106/sdks/sdk-core/src/entities/fractions/currencyAmount.ts#L23

Shout out to @gomesalexandre for catching this upgrade possibility . It would help rFOX by forcing us to be explicit in whether an amount is a base unit or precision with fromRawAmount / fromFractionalAmount.

But at a larger scale, better precision would be super helpful accross the apps scope now, and especially when we integrate something like #6981 .

AC:

• LOE and next steps from looking at the precision errors as a feature.
• Define API and / or library to use for this, present to team so we are all agree on solution.
• Create tickets for grooming/estimating