[GraphBolt] Hyperlink support in subgraph_sampler.

[yxy235]

Description

Doc: https://docs.google.com/document/d/18mKlawR2F_WT6VKPkaEBhHLAi65cbtdJfVtu811VwKo/edit?usp=sharing

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: 0804648

Build ID: 1

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

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Full logs path: link

[dgl-bot]

Commit ID: 69f268a

Build ID: 2

Status: ✅ CI test succeeded.

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[dgl-bot]

Commit ID: d402e97

Build ID: 3

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

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Full logs path: link

[dgl-bot]

Commit ID: 14a6284

Build ID: 4

Status: ❌ CI test failed in Stage [Torch CPU (Win64) Unit test].

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Full logs path: link

[dgl-bot]

Commit ID: 71e707f086d4211e79706c5ef296b15666dc1442

Build ID: 5

Status: ❌ CI test failed in Stage [Torch CPU (Win64) Unit test].

Report path: link

Full logs path: link

[dgl-bot]

Commit ID: a4ba7abb7543bb12b6eda5cbd9df669d53ff3cab

Build ID: 6

Status: ✅ CI test succeeded.

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Full logs path: link