Don't keep retrying expired withdraws

[DylanVerstraete]

Right now the code automically emits an event every X time to retry a withdraw transaction. We actually don't have to do that, we can just keep these in a seperate storage map and let the bridge daemons read from this map every X time. This will save some amount of work done on chain.

[DylanVerstraete]

This is also causing an issue on devnet: when stellar testnet is reset the bridge wallet is reset as well. Whenever someone tries to withdraw from the bridge, the transaction is retried forever until some tft is deposited back into the bridge.

[DylanVerstraete]

@robvanmieghem thoughts on this?