Use VaultIdManager instead of specific wallet when processing open requests

[ebma]

Follow-up to changes made in #385.

As pointed out in this comment, instead of passing a specific wallet instance we should pass an instance of the VaultIdManager so that all wallets are available.

We need to change the signature of spawn_tasks_to_execute_open_requests_async to receive a VaultIdManager instead of a wallet so that this logic works as expected if in the future we decide to support vault clients to use a different Stellar account per instance.

[ebma]

@pendulum-chain/product this task is about cleaning up some code and only becomes relevant once we want to give vault operators the chance to assign different Stellar accounts for each of their supported vaults (in one vault client instance). Thus it has rather low priority IMO.

[prayagd]

Hey team! Please add your planning poker estimate with Zenhub @adelarja @b-yap @ebma @TorstenStueber @gianfra-t

[annatekl]

@ebma @b-yap is this relevant to pick it up for the current spacewalk launch?

[ebma]

Not really @annatekl

[TorstenStueber]

@prayagd @annatekl Any reason this is not in Ready yet? Can we already move it there?

[prayagd]

Based on the comments above moving it to icebox as very low priority, correct if wrong @ebma