[1.x] Revert Fix memory leaks in Gluon in 1.x branch

[rondogency]

This reverts commit b523527.

This is a continuation of 1.7 revert of the same PR: #18692

Since CD is built on top of 1.x, we should also unblock CD on top of 1.7 release

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[leezu]

Instead of re-introducing the leak in 1.x branch, we can fix the pickle support by implementing __getstate__ and __setstate__ methods for _BlockScope.

[szha]

@leezu are you patching it in master? That way @rondogency can pick it up here and validate 1.x again.

[leezu]

The issue does not apply to master.

[szha]

Oh right, I just realized that _BlockScope is gone.

[leezu]

Let's revert first and merge again with the setstate and getstate fix; to ensure any development builds built from 1.x branch remain usable

[rondogency]

@mxnet-bot run ci [edge, unix-gpu]

[mxnet-bot]

Jenkins CI successfully triggered : [edge, unix-gpu]

[szha]

I think when enabling the branch protection, we accidentally turned on "Require branches to be up to date before merging". I'm requesting to disable it in https://issues.apache.org/jira/browse/INFRA-20616. Don't worry about updating the branch in this PR for now.