fix(registry): add timeout validation

[lftk]

使用 Consul 做服务发现时，如果 gRPC Client 的 timeout 设置为 0，程序会报错 discovery create watcher overtime。

原因是：

1. gRPC Client 会将 timeout 传给 discovery；

kratos/transport/grpc/client.go

Lines 190 to 196 in 861493a

	discovery.NewBuilder(
	options.discovery,
	discovery.WithInsecure(insecure),
	discovery.WithTimeout(options.timeout),
	discovery.WithSubset(options.subsetSize),
	discovery.PrintDebugLog(options.printDiscoveryDebugLog),
	)))

2. discovery 的 Build 会因为 timeout 为 0，立马超时，得到 ErrWatcherCreateTimeout 的错误。

kratos/transport/grpc/resolver/discovery/builder.go

Lines 97 to 102 in 861493a

	select {
	case <-done:
	err = watchRes.err
	case <-time.After(b.timeout):
	err = ErrWatcherCreateTimeout
	}

[shenqidebaozi]

This pull request includes several changes to improve the handling of timeouts and error checking in service resolution and gRPC resolver building. The most important changes include modifications to the resolve method in contrib/registry/consul/registry.go and the Build method in transport/grpc/resolver/discovery/builder.go.

Improvements to service resolution:

• contrib/registry/consul/registry.go: Added a conditional timeout to the resolve method, which now uses a new listServices function to handle service listing with or without a timeout. [1] [2]

Enhancements to gRPC resolver building:

• transport/grpc/resolver/discovery/builder.go: Modified the Build method to include a conditional timeout check, ensuring that the method properly handles the timeout scenario and waits for the operation to complete if no timeout is set.

Error handling improvements in tests:

• transport/grpc/resolver/discovery/builder_test.go: Updated the TestBuilder_Build test to correctly check for the absence of an error, ensuring the test's expected behavior aligns with the new implementation.