Consider pulling in PaymentDetails as an optional field inside QuoteDetails in Quote

[jiyoonie9]

From @diehuxx 's comment on discord

Is there any strong reason Quote has a payin and payout field with QuoteDetails and it has PaymentInstructions with a its payin and payout field? Is there a reason we didn't want to fold PaymentInstruction as an optional field in QuoteDetails? No push back, it seems like a small thing to me, but curious if there's a use case that informed keeping the two properties separate.
https://github.com/TBD54566975/tbdex/tree/main/specs/protocol#quote

[diehuxx]

Waiting until #206 is resolved to open PRs since this issue would create merge conflicts in the implementation changes. I have branches ready to PR as soon as #206 is done.

Spec change branch: https://github.com/TBD54566975/tbdex/compare/currency-199...quote-details-payment-instruction?expand=1
Javascript implementation change branch: https://github.com/TBD54566975/tbdex-js/compare/currency-199...quote-details?expand=1
Kotlin imeplementation change branch: https://github.com/TBD54566975/tbdex-kt/compare/currency-199...quote-details?expand=1

[diehuxx]

Ready for review.

Spec: #223
Javascript: TBD54566975/tbdex-js#140
Kotlin: TBD54566975/tbdex-kt#136