Added optional packet metadata to the packet and message types (backport #2305)

[mergify]

This is an automatic backport of pull request #2305 done by Mergify.
Cherry-pick of 82397d6 has failed:

On branch mergify/bp/release/v5.1.x/pr-2305
Your branch is up to date with 'origin/release/v5.1.x'.

You are currently cherry-picking commit 82397d6.
  (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:   docs/apps/transfer/events.md
	modified:   docs/apps/transfer/messages.md
	modified:   docs/ibc/proto-docs.md
	modified:   go.mod
	modified:   go.sum
	modified:   modules/apps/transfer/client/cli/tx.go
	modified:   modules/apps/transfer/ibc_module.go
	modified:   modules/apps/transfer/keeper/msg_server.go
	modified:   modules/apps/transfer/keeper/msg_server_test.go
	modified:   modules/apps/transfer/keeper/relay.go
	modified:   modules/apps/transfer/transfer_test.go
	modified:   modules/apps/transfer/types/events.go
	modified:   modules/apps/transfer/types/msgs.go
	modified:   modules/apps/transfer/types/msgs_test.go
	modified:   modules/apps/transfer/types/packet.go
	modified:   modules/apps/transfer/types/packet_test.go
	modified:   proto/ibc/applications/transfer/v1/tx.proto
	modified:   proto/ibc/applications/transfer/v2/packet.proto

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   modules/apps/29-fee/transfer_test.go
	both modified:   modules/apps/transfer/keeper/mbt_relay_test.go
	both modified:   modules/apps/transfer/keeper/relay_test.go
	both modified:   modules/apps/transfer/types/packet.pb.go
	both modified:   modules/apps/transfer/types/tx.pb.go
	deleted by us:   proto/ibc/applications/interchain_accounts/controller/v1/tx.proto

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

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[colin-axner]

I'll fix the conflicts