fix: consider Serverless prefix when invoking functions

[luislhl]

Motivation

Some parts of the code have hardcoded function prefixes, and we recently started allowing customizable prefixes

Acceptance Criteria

• The wallet-service and daemon packages should read the env var used to configure the prefix, with a default of hathor-wallet-service

TODO

• We should redeploy testnet-india after this PR is merged (lambdas and daemon, also check https://github.com/HathorNetwork/ops-tools/pull/1102)

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged
• Make sure either the unit tests and/or the QA tests are capable of testing the new features
• Make sure you do not include new dependencies in the project unless strictly necessary and do not include dev-dependencies as production ones. More dependencies increase the possibility of one of them being hijacked and affecting us.

[tuliomir]

question(non-blocking): Just double-checking that we won't be using the default 'hathor-wallet-service' prefix for testnet-india, right?

[luislhl]

Right, it was the first one where I tested a custom prefix