Auto merge of #119955 - kamalesh0406:master, r=WaffleLapkin

Modify GenericArg and Term structs to use strict provenance rules

This is the first PR to solve issue #119217 . In this PR, I have modified the GenericArg struct to use the `NonNull` struct as the pointer instead of `NonZeroUsize`. The change were tested by running `./x test compiler/rustc_middle`.

Resolves rust-lang/rust#119217

r? `@WaffleLapkin`

Author: bors