[Optimization] Use scipy's eigs instead of numpy in lap_pe

[BarclayII]

Fixes #5854.

[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: 556675034f464aab0da05edc203fdc41b46dbafe

Build ID: 2

Status: ⚪️ CI test cancelled due to overrun.

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[dgl-bot]

Commit ID: 7330fb967053e61c3e2a9aeb8631f278145defcd

Build ID: 3

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

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[dgl-bot]

Commit ID: 3f3b337a93c5691879b0a3e8876df690cf5b3e4b

Build ID: 4

Status: ❌ CI test failed in Stage [Tensorflow GPU Unit test].

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[dgl-bot]

Commit ID: 4a4112a735504f98ff38aab5adfe2ac270d2bd01

Build ID: 5

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

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[rudongyu]

Nice work! I'm fine with the other parts. Could you add an example in test_module_lap_pe to cover the case of k+1<n-1 ?

[dgl-bot]

Commit ID: b2e1ce18a8df1d94e47fd36ad7ad92353b208a8c

Build ID: 6

Status: ✅ CI test succeeded.

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[dgl-bot]

Commit ID: 71d9c736015d281d4bbf1bdddcd8e2632366e65b

Build ID: 7

Status: ✅ CI test succeeded.

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[dgl-bot]

Commit ID: 214494dddab733c60cb4d8ef1cbd61fa5872edae

Build ID: 8

Status: ✅ CI test succeeded.

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