Add Git submodules remote tracking

Add Git submodules remote tracking

* Always update the registered submodules using the remote-tracking branch
instead of the superproject's recorded SHA-1.
Only apply to the submodules' name that listed in the
`--submodules-remote-tracking` parameter, otherwise default behavior will be applied.

- Use case:
Update the latest registered configurations submodule from remote repository
- git-sync parameter:
./git-sync ... --submodules-remote-tracking="deployment-configs,app-configs"

Start by locating the command-line option parsing and the existing submodule update path in git-sync. Implement the requested remote-tracking behavior only for submodules named by the parameter, while preserving recorded-SHA behavior for all others; verify both paths against a remote repository with multiple submodules.

Written by the indexing model from the issue text.