feat(bank): Allow injectable restrictions on bank transfers (backport #14224)

[mergify]

This is an automatic backport of pull request #14224 done by Mergify.
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Changes to be committed:
	modified:   x/bank/README.md
	new file:   x/bank/keeper/export_test.go
	modified:   x/bank/keeper/keeper.go
	modified:   x/bank/keeper/keeper_test.go
	modified:   x/bank/keeper/send.go
	new file:   x/bank/types/restrictions.go
	new file:   x/bank/types/restrictions_test.go
	modified:   x/gov/testutil/expected_keepers_mocks.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.md

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[julienrbrt]

Let's wait after #17453 and more internal discussion and audit before merging this.

[julienrbrt]

Gentle ping @elias-orijtech

[elias-orijtech]

Sorry, I wasn't aware I held up the merge. The PR itself LGTM. I still think the proposed API makes it too easy to introduce incompatible restriction functions, but I suppose we can wait and see how it turns out.