Basic Info

Description of contribution in a few bullet points

This PR adds the feature to publish (on a latched topic) the is_active status message from the LifecycleManager.

Description of documentation updates required from your changes

N/A

Description of how this change was tested

Tested the feature in simulation the following scenarios:

1. With autostart set to false, is_active = False is published once on startup
   1. On calling the manage_nodes srv with command = STARTUP, is_active = True is published once when all the nodes are in active state
   2. When transitioning to another state using manage_nodes srv, is_active = False is published
2. With autostart set to true, is_active = False is published at LifecycleManager node startup. When all the nodes transition to active state, is_active = True is published once.

Future work that may be required in bullet points

N/A

For Maintainers:

• Check that any new parameters added are updated in docs.nav2.org
• Check that any significant change is added to the migration guide
• Check that any new features OR changes to existing behaviors are reflected in the tuning guide
• Check that any new functions have Doxygen added
• Check that any new features have test coverage
• Check that any new plugins is added to the plugins page
• If BT Node, Additionally: add to BT's XML index of nodes for groot, BT package's readme table, and BT library lists
• Should this be backported to current distributions? If so, tag with backport-*.