Remove roslib.load_manifest

[furushchev]

Loading this module is slow, especially on a slow disk I/O machine.
After profiling, I found the roslib.load_manifest crawls the workspace which slows down the importing.
In this PR, the function calls are removed, as the function is not required nowadays on the latest ROS distribution.

[furushchev]

@gbiggs Kindly ping to the maintainer

[furushchev]

@gbiggs Is this repository inactive? How can I proceed with the review process?

[furushchev]

@mjcarroll @gbiggs What is the maintenance status of this package?

[furushchev]

@mjcarroll @gbiggs It has been two weeks. Is there any progress?

[130s]

I'm not a maintainer though.

Such an old tradition I forgot what it was, looks like from pre-Catkin era (robotics.stackexchange.com#56413) so should not harm these days.

UPDATE Almost identical to #165

[mjcarroll]

@furushchev apologies for the delay. As noetic is reaching end-of-life in ~3 months, the ROS 1 repositories are much lower priority for maintenance.

[furushchev]

Thank you for your review!

As noetic is reaching end-of-life in ~3 months, the ROS 1 repositories are much lower priority for maintenance.

That makes sense. However, from 2023/9/25, when this PR was opened, the EOL was approximately 2 years away...
In any case, if there are no problems, please merge and release it