chore: add autoware_ prefix to the URL of gnss_poser

[TaikiYamada4]

Description

This PR is a counterpart of autowarefoundation/autoware.universe#8323 in autoware.universe.
The URL to gnss_poser is revised since the package name will change.
This PR should be merged after merging autowarefoundation/autoware.universe#8323.

Plus, I also wrote a caution that the example in directory-structure doesn't match the actual gnss_poser package.

TODO: Rename class name and file name in gnss_poser in autoware.universe to match the example.

• gnss_poser_core.cpp/hpp -> gnss_poser_node.cpp/hpp
• autoware::gnss_poser::GNSSPoser -> autoware::gnss_poser::GNSSPoserNode

Pre-review checklist for the PR author

The PR author must check the checkboxes below when creating the PR.

• I've confirmed the contribution guidelines.
• The PR follows the pull request guidelines.

In-review checklist for the PR reviewers

The Reviewers must check the checkboxes below before approval.

• The PR follows the pull request guidelines.

Post-review checklist for the PR author

The PR author must check the checkboxes below before merging.

• There are no open discussions or they are tracked via tickets.

After all checkboxes are checked, anyone who has write access can merge the PR.

[SakodaShintaro]

LGTM!