Vendor apple/containerization with a VM-extensions forwarding patch

Switch the containerization dependency from the github URL to a vendored copy
(third_party/containerization, upstream commit 6b7b42ca) referenced by path, so
we can carry a small local patch that upstream lacks: LinuxContainer.Configuration
gains a `vmExtensions` field forwarded into VMConfiguration.extensions. Upstream
already supports VMConfiguration.extensions + the VZInstanceExtension hook, but
LinuxContainer — our only entry point — never forwarded them, so there was no way
to attach a device (e.g. a memory balloon) to a container's VM.

Tests/, docs/, examples/, images/ and the corresponding test targets are trimmed
for footprint (we never build the dependency's tests). See PATCHES.md for the full
diff vs. upstream and the re-vendoring procedure. Also adds the ContainerizationExtras
product to NucleicCore (AddressAllocator, named in the configureVZ signature).

Co-Authored-By: Claude Opus 4.8 <[email protected]>

vminitd/.devcontainer/Dockerfile

@@ -0,0 +1,10 @@
+ARG SWIFT_VERSION=6.3.0
+FROM swift:${SWIFT_VERSION}-noble
+
+RUN apt-get update \
+&&  apt-get install make \
+&&  apt-get clean \
+&&  rm -rf /var/lib/apt/lists/*
+RUN swift sdk install \
+    https://download.swift.org/swift-6.3-branch/static-sdk/swift-6.3-DEVELOPMENT-SNAPSHOT-2026-03-05-a/swift-6.3-DEVELOPMENT-SNAPSHOT-2026-03-05-a_static-linux-0.1.0.artifactbundle.tar.gz \
+    --checksum f19419ad6a90d0fe5bbf8a28fbc47217ce212633c28257fc6549162558e6f9b6