feat: gRPC server for TxStatus endpoint (backport #3754)

[mergify]

Closes: #3753

This in some ways ties into #3421

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This is an automatic backport of pull request #3754 done by Mergify.

[mergify]

Cherry-pick of bb4f712 has failed:

On branch mergify/bp/v2.x/pr-3754
Your branch is up to date with 'origin/v2.x'.

You are currently cherry-picking commit bb4f7128.
  (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:
	new file:   app/grpc/tx/server.go
	new file:   app/grpc/tx/tx.pb.go
	new file:   app/grpc/tx/tx.pb.gw.go
	modified:   buf.yaml
	new file:   proto/celestia/core/v1/tx/tx.proto
	new file:   test/util/testnode/testnode_test.go

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   app/app.go
	both modified:   app/test/std_sdk_test.go
	deleted by them: app/test/testnode_test.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