[dynamo] Add asserts to prevent user defined objects/classes from going into ConstantVariable

[ezyang]

🐛 Describe the bug

This is the root cause of #110794 but it's a bit hard to educate everyone not to put random crap in ConstantVariable, so it would be good if we have more asserts that help people figure out.

Primary barrier to adding the assert is we'll probably have to fix a pile of latent bugs while we're at it.

cc @voznesenskym @penguinwu @EikanWang @jgong5 @Guobing-Chen @XiaobingSuper @zhuhaozhe @blzheng @wenzhe-nrv @jiayisunx @chenyang78 @kadeng @chauhang @Xia-Weiwen @aakhundov @Fidget-Spinner

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