Rollup merge of #132823 - RalfJung:conditional-const-calls, r=fee1-dead,compiler-errors

require const_impl_trait gate for all conditional and trait const calls

Alternative to rust-lang/rust#132786.

`@compiler-errors`  this is basically what I meant with my proposals. I found it's easier to express this in code than English. ;)

r? `@compiler-errors`

Author: workingjubilee