[Do not merge] [graphbolt] Disk feature fetcher

[xiangyuzhi]

Description

Disk feature store fetcher impl.
Based on pread now.
Performance test is ongoing. doc

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: 85f0cd768b318d63ef4ce7f40078d6a672b52113

Build ID: 1

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

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[dgl-bot]

Commit ID: c336470d234d4b2281c456d6da521f5e02e196d9

Build ID: 2

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

Report path: link

Full logs path: link

[dgl-bot]

Commit ID: b1d2ac994f04e5d272102b211a3602684a905fc7

Build ID: 3

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

Report path: link

Full logs path: link

[mfbalin]

@Rhett-Ying @xiangyuzhi is there going to be more progress on this PR? Looks like aio is supported from Linux 2.5, meaning it could be the fallback option when io_uring is unavailable.