Added standalone build for vpc-node & dstack-mesh

[Leechael]

Added standalone container build for vpc-node & dstack-mesh.

service-mesh

Propose to make it optional when users deploy CVM. When it's turned on, we launch the service mesh in the pre-launch script. This is to introduce it into dstack-os before it becomes stable.

Usage:

docker run -d --rm --name service-mesh -e DSTACK_GATEWAY_DOMAIN="dstack-pha-prod9.phala.network" \
-v /var/run/dstack.sock:/var/run/dstack.sock -v /dstack/dstack-mesh:/var/lib/dstack-mesh \
-p 127.0.0.1:8091:8091 service-mesh:latest

vpc-node

The Tailscale client that auto-logs into a specified Headscale server with mTLS authentication through a service mesh.

Usage:

docker run -d --name vpc-node --cap-add NET_ADMIN \
--device /dev/net/tun:/dev/net/tun --network host \
-e NODE_NAME="<NODE_NAME>" \
-e VPC_SERVER_HOST="<app-id>-443s.<gateway-domain>" \
-v /var/lib/vpc-node:/var/lib/vpc-node vpc-node:latest

This also exposes a debug endpoint for metrics:

• http://localhost:9002/debug/metrics
• http://localhost:9002/debug/pprof
• http://localhost:9002/debug/ipn
• http://localhost:9002/debug/magicsock

Additional Note

This PR also depends on #22, which extends the ability to build VPCs across different gateways.

[Leechael]

Refactor: #26