[v1.x] Add ONNX model support matrix

[waytrue17]

Description

Add ONNX model support matrix and a tool that helps generate the matrix.

Checklist

Essentials

• PR's title starts with a category (e.g. [BUGFIX], [MODEL], [TUTORIAL], [FEATURE], [DOC], etc)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage
• Code is well-documented

Changes

• Feature1, tests, (and when applicable, API doc)
• Feature2, tests, (and when applicable, API doc)

Comments

• If this change is a backward incompatible change, why must this change be made.
• Interesting edge cases to note here

[mxnet-bot]

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[Zha0q1]

Shall we link to GluonCV pretained model page here? wdyt
Sorry about the late review, we can also do this in another pr and merge this one

[waytrue17]

Sure, added link to both gluoncv and gluonnlp

[Zha0q1]

LGTM!