feat: Add convenience method for constructing key to access account's…

… balance for a given denom (backport cosmos#12674) (cosmos#12745)

* feat: Add convenience method for constructing key to access account's balance for a given denom (cosmos#12674)

This PR adds a convenience method for constructing the key necessary to query for the account's balance of a given denom.

I ran into this issue since we are using ABCI query now to perform balance requests because we are also requesting merkle proofs for the returned balance [here](https://github.com/celestiaorg/celestia-node/pull/911/files#diff-0ee31f5a7bd88e9f758e6bebdf3ee36365519e55a451098d9638c39afe5eac42R144).

It would be nice to have a definitive convenience method for constructing the key.

[Ref.](github.com/celestiaorg/celestia-node/pull/911)

(cherry picked from commit a1777a8)

# Conflicts:
#	CHANGELOG.md
#	x/bank/legacy/v043/store.go
#	x/bank/types/keys.go

* Update CHANGELOG.md

* fix conflict

Co-authored-by: rene <41963722+renaynay@users.noreply.github.com>
Co-authored-by: Marko <marbar3778@yahoo.com>

CHANGELOG.md

@@ -47,6 +47,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (x/params) [#12724](https://github.com/cosmos/cosmos-sdk/pull/12724) Add `GetParamSetIfExists` function to params `Subspace` to prevent panics on breaking changes.
 * [#12668](https://github.com/cosmos/cosmos-sdk/pull/12668) Add `authz_msg_index` event attribute to message events emitted when executing via `MsgExec` through `x/authz`.
 * [#12697](https://github.com/cosmos/cosmos-sdk/pull/12697) Upgrade IAVL to v0.19.0 with fast index and error propagation. NOTE: first start will take a while to propagate into new model.
+* (x/bank) [#12674](https://github.com/cosmos/cosmos-sdk/pull/12674) Add convenience function `CreatePrefixedAccountStoreKey()` to construct key to access account's balance for a given denom.
 
 ### Bug Fixes