[Request]: Pre-warmed Micro-VM pool to reduce container cold-start latency

### Feature or enhancement request details

### Feature or enhancement request details
Currently, `apple/container` spins up a completely fresh micro-VM using the macOS Virtualization framework for every individual container. While this architecture offers unparalleled isolation, it introduces a noticeable cold-start latency overhead of roughly **~0.9 seconds** per container launch.

In contrast, platforms like Docker Desktop utilize a pre-warmed, shared background virtual machine, allowing them to spin up containers in **~0.2 seconds**. For local development environments that involve frequent container restarts, short-lived tasks, or scripting automation, this latency difference accumulates quickly and compromises the developer experience.

### Proposed Solution
I would like to see an optional optimization framework implemented into the underlying `Containerization` Swift library to drastically cut down container spin-up times. Two potential paths could achieve this:

1. **Pre-warmed Micro-VM Pool**: Keep a configurable number (e.g., a pool of 1 or 2) of generalized, generic micro-VM instances booted and "warm" in the background. When a user runs a container, the tool can instantly inject the OCI image layer and environment configurations into an already-running VM instance, slashing launch time to sub-200ms.
2. **Shared VM Configuration Profile**: Provide a configuration flag (e.g., `--shared-vm` or a global configuration option) allowing users to intentionally trade off absolute isolation in exchange for raw speed. This would let multiple containers share a single, long-running Virtualization framework VM instance, mirroring the traditional container layout.

### Alternatives considered
* Leaving the architecture as-is, which forces developers running high-frequency short-lived tasks to stick with Docker Desktop, OrbStack, or Colima.
* Manually keeping containers alive in a sleep loop, which wastes local CPU and memory resources unnecessarily.

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

The request targets the underlying Containerization Swift library, but it names no files, tests, or entry points. Start by tracing how apple/container creates a fresh micro-VM through the macOS Virtualization framework, then determine the design and tests needed for pooling or shared VM configuration. Done should include an agreed scope, isolation behavior, configuration surface, and cold-start validation.

Written by the indexing model from the issue text.