Auto merge of #125928 - michaelwoerister:fix-cgu-hashstable, r=oli-obk

Stabilize order of MonoItems in CGUs and disallow query_instability lint for rustc_monomorphize

The HashStable impl for `CodegenUnit` was incorrect as described in [MCP 533](rust-lang/compiler-team#533). This PR removes any indeterminism from the way codegen units are built. The changes are pretty straightforward.

Part of rust-lang/rust#84447 and [MCP 533](rust-lang/compiler-team#533).