Add gRPC P2P host transport

[Ayush3941]

Whats this Pr does

Adds gRPC as a third FSC node-to-node P2P transport alongside libp2p and WebSocket.
The implementation adds a new platform/view/services/comm/host/grpc transport, wires it through fsc.p2p.type=grpc, and keeps the existing Comm/session/view flow unchanged.

What changed

• added gRPC P2PHost implementation
• wired fsc.p2p.type=grpc
• added fsc.p2p.opts.grpc.* config
• enforced mTLS and peer identity binding for gRPC streams
• added NWO wiring and gRPC-focused integration coverage
• added gRPC transport docs

closes #1026

Validation

Passed locally:

• go test ./platform/view/services/comm/host/grpc/...
• gRPC integration/fsc/pingpong
• gRPC integration/fsc/stoprestart
• gRPC integration/fabric/iou

[github-actions]

Hey @Ayush3941 👋 thanks for the PR!
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• aef9325 add grpc p2p host transport
• 7abe857 add grpc p2p host transport v2
• d01aa2b add grpc p2p host transport v3
• 99e3bce add grpc p2p host transport v4

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[github-actions]

Hi @Ayush3941 👋 — the recent merge of PR #1534 has introduced a merge conflict in this PR. Please resolve the merge conflict so that this PR can be reviewed again. Thank you!