Rust 1.78 Upgrade For Linux 6.10, Dropping In-Tree "alloc" Fork To Save ~10k Lines

There's another Rust upgrade coming for the Linux 6.10 kernel to bump the Rust version baseline required for building the Rust in-tree kernel components. This raising of the baseline will continue until a suitable minimum version is achieved where official Rust compiler "just works" well with the Rust'ed kernel bits. The Rust upgrade in Linux 6.10 also does away with its in-tree "alloc" fork for big code savings and simplifying maintenance.

Dropping the in-tree "alloc" fork for Rust means around ~10k lines of code has been dropped and also eases Rust version upgrades moving forward. This also increases the likelihood that newer Rust compiler versions will work better with the Linux kernel code.The hope is in the "near future" to be able to define the minimum Rust version for building the kernel.

The Rust changes for Linux 6.10 also include supporting DWARFv5, supporting Zlib and Zstd debuginfo compression, and a number of kernel crate improvements.

More details on the upgraded Rust code for Linux 6.10 via this pull request.