feat: add timeout for DialContext

[szza]

1. Are you opening this pull request for bug-fix, optimization or new feature?

• new feature

2. Please describe how these code changes achieve your intention.

use gent/client to dial remote with timeout

3. Please link to the relevant issues (if any).

4. What documentation changes (if any) need to be made/updated because of this PR?

4. Checklist

• I have squashed all insignificant commits.
• I have commented my code for explaining package types, values, functions, and non-obvious lines.
• I have written unit tests and verified that all tests passes (if needed).
• I have documented feature info on the README (only when this PR is adding a new feature).
• (optional) I am willing to help maintain this change if there are issues with it later.

[panjf2000]

Thanks for the PR! But I don't think we need this new method as we can call net.DialTimeout and then call gnet.Client.EnrollContext.