compiler: Improve scalar aliases detection and scheduling

[mloubout]

Quite a few more changes that I would have liked but this avoid being too drastic. This basically make scalar aliases more reobust

• Remove guards from scalar aliases used in multiple clusters to avoid issue with scope of variable
• No longer allow scalar aliases that depend on a condition
• Make aliases const (tiny change but bit better technically)
• Small fix on lifting that prevents detaching scalar clusters from cluster with same guard
• Tiny change to cse dtype due to numpy integer upcasting

[review-notebook-app]

Check out this pull request on 

See visual diffs & provide feedback on Jupyter Notebooks.

---

Powered by ReviewNB

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.00%. Comparing base (8ad5ec1) to head (1a3141e).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2858      +/-   ##
==========================================
+ Coverage   78.96%   79.00%   +0.03%     
==========================================
  Files         248      248              
  Lines       51089    51167      +78     
  Branches     4422     4427       +5     
==========================================
+ Hits        40344    40422      +78     
+ Misses       9937     9935       -2     
- Partials      808      810       +2     

☔ 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.