Rollup merge of #37336 - michaelwoerister:debuginfo-type-ids, r=eddyb

debuginfo: Use TypeIdHasher for generating global debuginfo type IDs.

The only requirement for debuginfo type IDs is that they are globally unique. The `TypeIdHasher` (which is used for `std::intrinsic::type_id()` provides that, so we can get rid of some redundancy by re-using it for debuginfo. Values produced by the `TypeIdHasher` are also more stable than the current `UniqueTypeId` generation algorithm produces -- these incorporate the `NodeId`s, which is not good for incremental compilation.

@alexcrichton @eddyb : Could you take a look at the endianess adaptations that I made to the `TypeIdHasher`?

Also, are we sure that a 64 bit hash is wide enough for something that is supposed to be globally unique? For debuginfo I'm using 160 bits to make sure that we don't run into conflicts there.