fix: use 127.0.0.1 instead of localhost as default HostPort for IPv4 consistency

[AmitThakkar]

What was changed

Updated the defaultHostPort constant in internal/grpc_dialer.go from:

const defaultHostPort = "localhost:7233"

to:

const defaultHostPort = "127.0.0.1:7233"

to ensure consistent and reliable connectivity in local development environments across platforms.

Why?

The default HostPort value used when connecting to the Temporal server is set to "localhost:7233". However, "localhost" may resolve to ::1 (IPv6) on some systems, while temporal server start-dev binds only to 127.0.0.1 (IPv4).

This mismatch leads to errors like:

failed reaching server: context deadline exceeded

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[cretz]

I am concerned this is a backwards incompatible change. If we had the SDK to design again, we probably wouldn't even have a default host:port, we'd require it be set by users (and this is what we do in newer SDKs). In the meantime, we encourage explicitly setting this value to what you need it to be and not relying on the default. I understand that samples rely on the default, but they are meant to be adapted as needed.