Fix nix build

[P1n3appl3]

This fixes some of the remaining issues to get the nix build passing again:

• issue with the cargo bundle patch (fixed in nix: Fix the cargo-bundle override #28061)
• outdated version of libwebrtc from nixpkgs
• chore: Bump Rust version to 1.86 #28021 bumped the rust toolchain version and we need to bump the rust-overlay flake input to have that new one available.

Release Notes:

• N/A