Auto merge of #116767 - cjgillot:alloc-normalize, r=oli-obk

Normalize alloc-id in tests.

AllocIds are globally numbered in a rustc invocation. This makes them very sensitive to changes unrelated to what is being tested. This commit normalizes them by renumbering, in order of appearance in the output.

The renumbering allows to keep the identity, that a simple `allocN` wouldn't. This is useful when we have memory dumps.

cc `@saethlin`
r? `@oli-obk`

Author: bors