Endpoint to trigger contract recovery
Description of Feature
This MR adds a new API endpoint which allows the user to trigger a rescan of the blockchain to find recoverable file contracts.
Description of Work Flow
The user calls the POST endpoint /renter/initrecovery which starts a recovery thread in the background if the wallet is unlocked. (Otherwise the contractor can't fetch the seed)
Modules and Packages Impacted
renter, renter/contractor, siatest/renter