Rollup merge of #122370 - gurry:122199-ice-unexpected-node, r=davidtwco

Gracefully handle `AnonConst` in `diagnostic_hir_wf_check()`

Instead of running the WF check on the `AnonConst` itself we run it on the `ty` of the generic param of which the `AnonConst` is the default value.

Fixes #122199

Author: matthiaskrgr