refactor: remove lifecycle predicates and add lifecycle state getter

[domire8]

Description

As title suggests.
For the lifecycle state getter, I made an enum in modulo core because I feel like the ROS PRIMARY_STATE_XXX is too verbose and has a long name/namespace.

Review guidelines

Estimated Time of Review: 10 minutes

Checklist before merging:

• Confirm that the relevant changelog(s) are up-to-date in case of any user-facing changes

[eeberhard]

I don't think that adding a wrapper enum for the primary states is particularly useful, especially if you hide all the transition states as "UNKNOWN".
I think the main use case for a component to check its own state is during parameter validation callback, which will usually happen during a primary state like inactive. But, this is also something that might feasibly happen during transition states, for example by internally setting a parameter during on_activate; treating transition states as UNKNOWN states would then make it less clear.

The underlying lifecycle node already has get_current_state() which you use here, and I think returning the rclcpp_lifecycle::State is already very useful (because you can get id() for switch cases and label() for logging). If you really want, you could just wrap the get_current_state() method with get_lifecycle_state(), but keep the same return type.

I would prefer to have this PR just remove the lifecycle predicate.

[domire8]

Okay, I added a wrapper. It's just quite complicated to use really IMO because the return type rclcpp_lifecycle::State is different from the enum type lifecycle_msgs::msg::State::XXX

[eeberhard]

it's just quite complicated to use really IMO because the return type rclcpp_lifecycle::State is different from the enum type lifecycle_msgs::msg::State::XXX

I do agree that using the lifecycle_msgs::msgs::State::XXX is quite verbose, but again I wouldn't suggest redefining the existing standard if it leads to a loss of information with no other real gain, especially as we get both id() and label() from the State class.