Injectable restrictions

[jiujiteiro]

Description

1- Provides a mechanism for injecting functions that can restrict bank transfers.
2- Updates InputOutputCoins to take in a single Input. This was originally done with cosmos#12610 which was partially reverted with cosmos#12670. The revert was needed because a breaking change had been made in the protos, but for some reason reverted more than what was needed. MsgMultiSend allows for only one input, but InputOutputCoins still allowed for multiple. For this change, a single input is needed in InputOutputCoins due to the complexity that would be added if still allowing for multiple inputs.

---

Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• followed the guidelines for building modules
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all CI checks have passed

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)