fix: panic protection for DenomResolver (backport #104)

[mergify]

Closes BLO-1340

Remove GetDenomResolver function and always use ResolveToDenom which includes nil protection.

---

This is an automatic backport of pull request #104 done by Mergify.

[mergify]

Cherry-pick of bcd3fc7 has failed:

On branch mergify/bp/sdk-47/pr-104
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Changes to be committed:
	modified:   Makefile
	modified:   go.mod
	modified:   tools/tools.go
	modified:   x/feemarket/ante/expected_keepers.go
	modified:   x/feemarket/ante/fee.go
	modified:   x/feemarket/ante/mocks/mock_bank_keeper.go
	modified:   x/feemarket/ante/mocks/mock_feegrant_keeper.go
	modified:   x/feemarket/ante/mocks/mock_feemarket_keeper.go
	modified:   x/feemarket/keeper/feemarket.go
	modified:   x/feemarket/keeper/keeper.go
	modified:   x/feemarket/post/expected_keeper.go
	modified:   x/feemarket/post/mocks/mock_bank_keeper.go
	modified:   x/feemarket/post/mocks/mock_feegrant_keeper.go
	modified:   x/feemarket/post/mocks/mock_feemarket_keeper.go
	modified:   x/feemarket/types/errors.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   go.sum
	both modified:   x/feemarket/ante/mocks/mock_account_keeper.go
	both modified:   x/feemarket/post/mocks/mock_account_keeper.go
	both modified:   x/feemarket/types/mocks/mock_account_keeper.go

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally