cargo: bump MSRV to 1.90.0

[HuijingHei]

No description provided.

[gemini-code-assist]

Code Review

This pull request correctly bumps the Minimum Supported Rust Version (MSRV) to 1.90.0. The changes in Cargo.toml and the corresponding documentation update in docs/release-notes.md are appropriate and consistent. To ensure the project remains in a consistent state, I recommend also running cargo update to regenerate the Cargo.lock file against the new MSRV. Additionally, it would be beneficial to verify that the Rust toolchain version used in the CI/CD pipelines is updated to 1.90.0 or newer to match this change.

[HuijingHei]

Hold on, maybe the CI could be simpler once we have coreos/coreos-ci-lib#167

[HuijingHei]

Looks these tests are also need none root.

[2026-01-06T13:50:12.121Z] Running test: iso-offline-install-iscsi.ibft.uefi
[2026-01-06T13:50:12.121Z] [2026-01-06T13:50:03Z ERROR virtiofsd] can't apply the child capabilities: failed to sync capabilities with the kernel
[2026-01-06T13:50:12.121Z] qemu-system-x86_64: -chardev socket,id=virtiofschar0,path=/var/tmp/mantle-qemu1668519661/virtiofsd-0.sock: Failed to connect to '/var/tmp/mantle-qemu1668519661/virtiofsd-0.sock': Connection refused
[2026-01-06T13:50:33.971Z] FAIL: iso-offline-install-iscsi.ibft.uefi (0s)
[2026-01-06T13:50:33.971Z]     running iso: failed to establish qmp connection: dial unix /var/tmp/mantle-qemu1668519661/qmp-1767707403515000315.sock: connect: connection refused
[2026-01-06T13:50:33.971Z] Running test: iso-offline-install-iscsi.ibft-with-mpath.bios
[2026-01-06T13:50:34.894Z] [2026-01-06T13:50:34Z ERROR virtiofsd] can't apply the child capabilities: failed to sync capabilities with the kernel
[2026-01-06T13:50:35.818Z] qemu-system-x86_64: -chardev socket,id=virtiofschar0,path=/var/tmp/mantle-qemu1801902470/virtiofsd-0.sock: Failed to connect to '/var/tmp/mantle-qemu1801902470/virtiofsd-0.sock': Connection refused
[2026-01-06T13:51:07.810Z] FAIL: iso-offline-install-iscsi.ibft-with-mpath.bios (0s)
[2026-01-06T13:51:07.810Z]     running iso: failed to establish qmp connection: dial unix /var/tmp/mantle-qemu1801902470/qmp-1767707434722018814.sock: connect: connection refused
[2026-01-06T13:51:07.810Z] Running test: iso-offline-install-iscsi.manual.bios
[2026-01-06T13:51:07.810Z] [2026-01-06T13:51:05Z ERROR virtiofsd] can't apply the child capabilities: failed to sync capabilities with the kernel
[2026-01-06T13:51:07.810Z] qemu-system-x86_64: -chardev socket,id=virtiofschar0,path=/var/tmp/mantle-qemu3918585589/virtiofsd-0.sock: Failed to connect to '/var/tmp/mantle-qemu3918585589/virtiofsd-0.sock': Connection refused
[2026-01-06T13:51:39.808Z] FAIL: iso-offline-install-iscsi.manual.bios (0s)
[2026-01-06T13:51:39.808Z]     running iso: failed to establish qmp connection: dial unix /var/tmp/mantle-qemu3918585589/qmp-1767707465898579044.sock: connect: connection refused