Fix internal state machine of action node

[Oberacda]

The implicit state machine in the action node was not implemented correctly.
This PR implements the state machine explicitly and fixes the invalid transitions in the previous one.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 24.44444% with 68 lines in your changes are missing coverage. Please review.

Project coverage is 33.02%. Comparing base (17e31b8) to head (4d8754c).

Files	Patch %	Lines
ros_bt_py/src/ros_bt_py/ros_nodes/action.py	24.44%	68 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev      #63      +/-   ##
==========================================
+ Coverage   32.87%   33.02%   +0.15%     
==========================================
  Files          37       37              
  Lines        5415     5453      +38     
  Branches     1250     1251       +1     
==========================================
+ Hits         1780     1801      +21     
- Misses       3567     3584      +17     
  Partials       68       68              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[github-actions]

Test Results

 10 files  ±0   10 suites  ±0   5s ⏱️ ±0s
153 tests ±0  153 ✅ ±0  0 💤 ±0  0 ❌ ±0 
306 runs  ±0  306 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 4d8754c. ± Comparison against base commit 17e31b8.

♻️ This comment has been updated with latest results.

[nspielbau]

LGTM