Report skipped step state as soon as it's determined

[6543]

currently we mark all steps that are pending after a workflow finished as skipped.

this is wrong!

as we know when we decide if a step is skipped we now just signal that back the server.

this pull also rewords the pipeline/state.State to match our terminology

[lafriks]

Apart from lint failures LGTM

[codecov]

Codecov Report

❌ Patch coverage is 37.73585% with 33 lines in your changes missing coverage. Please review.
✅ Project coverage is 33.06%. Comparing base (6d60849) to head (df9a6b3).
⚠️ Report is 18 commits behind head on main.

Files with missing lines	Patch %	Lines
agent/tracer.go	0.00%	20 Missing ⚠️
server/pipeline/step_status.go	60.00%	5 Missing and 1 partial ⚠️
pipeline/tracing/tracer.go	0.00%	4 Missing ⚠️
pipeline/runtime/executor.go	78.57%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6295      +/-   ##
==========================================
+ Coverage   32.43%   33.06%   +0.63%     
==========================================
  Files         420      420              
  Lines       28320    28333      +13     
==========================================
+ Hits         9185     9368     +183     
+ Misses      18286    18103     -183     
- Partials      849      862      +13     

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[6543]

regression is fixed with #6300 (also code simplified and more tests)