Fluss Documentation add CoordinatorServer High Availability (HA) Setup

[striver619]

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(The sections below can be removed for hotfixes or typos)
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Purpose

This PR adds support for CoordinatorServer High Availability (HA) by providing deployment
documentation. It covers how to deploy a distributed Fluss cluster with multiple CoordinatorServers
using ZooKeeper-based leader election, ensuring failover when the primary CoordinatorServer fails.

Linked issue: close #3989

Brief change log

• Added deploying-distributed-cluster.md — guide for deploying a distributed Fluss cluster
  on bare machines, including multi-CoordinatorServer HA configuration
• Added deploying-with-docker.md — guide for deploying Fluss with Docker and Docker Compose,
  including multi-CoordinatorServer HA and multi-TabletServer setups

Tests

N/A — this is a documentation-only change.

API and Format

N/A — no code changes, only new documentation files.

Documentation

This PR introduces two new documentation pages:

• Deploying Distributed Cluster (bare metal deployment guide with CoordinatorServer HA)
• Deploying with Docker (Docker and Docker Compose guide with CoordinatorServer HA)

[striver619]

@wuchong @luoyuxia Appreciate a review here.