[GraphBolt] Modify exclude_seed_edges to support seeds.

[yxy235]

Description

1. Add add_reverse_edges_2 to support seeds format.
2. Add _exclude_homo_edges to support seeds format.
3. Add tests to test function in utils.py.

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]

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[dgl-bot]

Commit ID: bf150a79e27d0a25e0fc420b363fbc45de773c8e

Build ID: 1

Status: ⚪️ CI test cancelled due to overrun.

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Commit ID: a18a603

Build ID: 2

Status: ✅ CI test succeeded.

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Commit ID: ea848d5

Build ID: 3

Status: ❌ CI test failed in Stage [Torch CPU Example test].

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[yxy235]

@dgl-bot

[dgl-bot]

Commit ID: ea848d5

Build ID: 4

Status: ✅ CI test succeeded.

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