Repo: Delete vMCR

[smalis-msft]

Now that the proper version of the feature has shipped this is no longer needed or being used.

[github-actions]

⚠️ Unsafe Code Detected

This PR modifies files containing unsafe Rust code. Extra scrutiny is required during review.

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[Copilot]

Pull request overview

This PR removes the unused “vMCR” device plumbing from the workspace now that the shipped implementation has superseded it.

Changes:

• Deletes the mcr_resources crate and removes it from the workspace dependency list/lockfile.
• Removes the OpenVMM CLI flag (--mcr) and the associated device instantiation code path.
• Removes the Underhill/OpenHCL environment option and instantiation logic for the MCR device.

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
vm/devices/mcr_resources/src/lib.rs	Removes the MCR resource handle type (crate deleted).
vm/devices/mcr_resources/Cargo.toml	Removes the mcr_resources crate manifest (crate deleted).
openvmm/openvmm_entry/src/lib.rs	Drops the opt.mcr-gated VPCI device injection.
openvmm/openvmm_entry/src/cli_args.rs	Removes the --mcr CLI flag definition.
openvmm/openvmm_entry/Cargo.toml	Removes the mcr_resources dependency.
openhcl/underhill_core/src/worker.rs	Removes MCR controller injection into controllers.vpci_devices; cleans up now-unneeded mutability.
openhcl/underhill_core/src/options.rs	Removes OPENHCL_MCR_DEVICE parsing and the mcr option field.
openhcl/underhill_core/src/lib.rs	Removes propagation of the mcr option into UnderhillEnvCfg.
openhcl/underhill_core/Cargo.toml	Removes the mcr_resources dependency.
Cargo.toml	Removes mcr_resources from workspace dependencies.
Cargo.lock	Removes the mcr_resources package entry and references from dependents.