Introduce Metadata-based Service Registration, Routing and Load Balancing for Seata

### Check Ahead

- [x] I have searched the [issues](https://github.com/seata/seata/issues) of this repository and believe that this is not a duplicate.

- [x] I am willing to try to implement this feature myself.

### Why you need it?

In the existing Seata service registration and discovery system:

+ There is a **lack of differentiation information between server instances,** limiting clients to random/round-robin load balancing based on IP and port.

+ It cannot support:

- Metadata-based load balancing strategies such as weighted random.

- Region/data center routing, version, capability, and environment isolation, and more granular canary and evolution strategies.

### How it could be?

Introduce a **metadata-based service registration and discovery mechanism**:

+ Metadata-aware **load balancing capabilities**

+ Configurable and composable **routing filtering mechanism**

While maintaining **full compatibility with existing registration and discovery behavior**, it provides Seata with higher-level service governance capabilities.

### Other related information

_No response_