Rollup merge of #120970 - RalfJung:static-promoted-test, r=oli-obk

add another test for promoteds-in-static

rust-lang/rust#119614 led to validation of promoteds recursing into statics. These statics can point to `static mut` and interior mutable `static` and do other things we don't allow in `const`, but promoteds are validated as `const`, so we get strange errors (saying "in `const`" when there is no const) and surprising validation failures.

rust-lang/rust#120960 fixes that; this here adds another test.

r? ``@oli-obk``
Fixes rust-lang/rust#120968