[sBTC DR 0.2] Add support for stx withdrawal

[friedger]

Description

The SIP for Nakamoto sBTC describes sBTC withdrawal as stacks transactions.

sBTC DR should support the same.

Context

https://github.com/stacksgov/sips/blob/31dae06bc9c18fa4a7ef43cf7387e83a650228f6/sips/sip-025/sip-025-sbtc.md

Expected Approach

Add function request-withdrawal to asset.clar that allows to initiate a withdrawal as a stx transaction.

Ideally, asset.clar should be refactored to be upgradable.

Romeo should observe the stacks chain for withdrawal request and initiate a burn and withdrawal.

Acceptance Criteria

• [ ] User can send withdrawal request on stx chain via bridge web app and receives btc on btc chain.