[GraphBolt] Fix DiskBasedFeature Memory Leak Problem

[pyynb]

Description

Checklist

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [$CATEGORY] (such as [NN], [Model], [Doc], [Feature]])
• I've leverage the tools to beautify the python and c++ code.
• The PR is complete and small, read the Google eng practice (CL equals to PR) to understand more about small PR. In DGL, we consider PRs with less than 200 lines of core code change are small (example, test and documentation could be exempted).
• All changes have test coverage
• Code is well-documented
• To the best of my knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change
• Related issue is referred in this PR
• If the PR is for a new model/paper, I've updated the example index here.

Changes

[dgl-bot]

To trigger regression tests:

• @dgl-bot run [instance-type] [which tests] [compare-with-branch];
  For example: @dgl-bot run g4dn.4xlarge all dmlc/master or @dgl-bot run c5.9xlarge kernel,api dmlc/master

[dgl-bot]

Commit ID: 79368c3

Build ID: 1

Status: ❌ CI test failed in Stage [Lint Check].

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[dgl-bot]

Commit ID: 14092b9

Build ID: 2

Status: ⚪️ CI test cancelled due to overrun.

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[dgl-bot]

Commit ID: ef30637

Build ID: 3

Status: ✅ CI test succeeded.

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[dgl-bot]

Commit ID: a6cc2e36fc9aa043c4b8e7e5a9223c95e7bdfd1d

Build ID: 4

Status: ✅ CI test succeeded.

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[Rhett-Ying]

have you benchmarked the new implementation? Is it the same implementation as previous one which obtained previous benchmark results?

[dgl-bot]

Commit ID: e0c7c0e9952fb069e2118ceaa700b80d94d1c267

Build ID: 5

Status: ✅ CI test succeeded.

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[dgl-bot]

Commit ID: 422bd60a21e050d3681aa8c4e6c04e204e149a1a

Build ID: 6

Status: ⚪️ CI test cancelled due to overrun.

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[dgl-bot]

Commit ID: cffc20e846641adfa8c07720e153c9a7970344b3

Build ID: 7

Status: ⚪️ CI test cancelled due to overrun.

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[dgl-bot]

Commit ID: 2d36edcbe58468e7a33ddf3f7ff5b98df3eb063b

Build ID: 8

Status: ⚪️ CI test cancelled due to overrun.

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[dgl-bot]

Commit ID: 6443d998377878b8a3f0a2e982e46b79b9b95785

Build ID: 9

Status: ⚪️ CI test cancelled due to overrun.

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[dgl-bot]

Commit ID: a88145a5b432692123dacf2ccf8bba2ec696d0b1

Build ID: 10

Status: ✅ CI test succeeded.

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