feat: decouple cosmos-db (backport #874)

[mergify]

This is an automatic backport of pull request #874 done by Mergify.
Cherry-pick of 11ba496 has failed:

On branch mergify/bp/release/v1.x.x/pr-874
Your branch is up to date with 'origin/release/v1.x.x'.

You are currently cherry-picking commit 11ba496.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   Makefile
	modified:   basic_test.go
	modified:   batch_test.go
	modified:   benchmarks/bench_test.go
	modified:   benchmarks/cosmos-exim/main.go
	modified:   cmd/iaviewer/main.go
	new file:   db/memdb.go
	new file:   db/types.go
	new file:   db/wrapper.go
	modified:   diff_test.go
	modified:   export.go
	modified:   export_test.go
	modified:   go.mod
	modified:   immutable_tree.go
	modified:   import_test.go
	modified:   internal/bytes/bytes.go
	modified:   iterator_test.go
	modified:   migrate_test.go
	modified:   mock/db_mock.go
	modified:   mutable_tree.go
	modified:   mutable_tree_test.go
	modified:   nodedb_test.go
	modified:   proof_iavl_test.go
	modified:   proof_ics23_test.go
	modified:   testutils_test.go
	modified:   tree_random_test.go
	modified:   tree_test.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .github/workflows/lint.yml
	both modified:   batch.go
	both modified:   nodedb.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

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[alexanderbez]

ACK (pending conflict resolution)