fixes #23564; `hasCustomPragma` skips alises types

[ringabout]

fixes #23564

perhaps handle generic aliases (tyGenericInst for aliases types) if needed

[ringabout]

It seems that we need to add an internal version of getTypeInst to skip aliases types

[metagn]

I would think it should be exposed to users as well. The first way I thought of doing it was to go in the impl for the type alias sym and recurse with the body as the type instead, but the body (Sym "T0") just has the alias type (T) as its sym which gets used by getTypeInst and causes a loop. Maybe skipAlias or something more general can be exposed instead. (might be fine to specialize since getType never represents a tyAlias).

[ringabout]

Okay, I will add something like getTypeInstSkipAlias to skip aliases

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