Replace clang-format with AStyle for code formatting

[harrylin98]

This is a prototype PR to address the issue #3450

clang-format is too prescriptive, it actively removes intentional alignment (column-aligned declarations, assignments, multi-line conditions) rather than leaving them alone.

AStyle is less aggressive and preserves developer formatting choices while still enforcing consistent indentation, spacing, and pointer alignment.

Commits:

1. Replace clang-format with AStyle (config, CI workflow, docs)
2. TODO: Apply AStyle formatting to all source and unit test files under src/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.36%. Comparing base (d2db0c2) to head (11c8eff).
⚠️ Report is 11 commits behind head on unstable.

Additional details and impacted files

@@            Coverage Diff            @@
##           unstable    #3560   +/-   ##
=========================================
  Coverage     76.35%   76.36%           
=========================================
  Files           159      159           
  Lines         80054    80054           
=========================================
+ Hits          61125    61131    +6     
+ Misses        18929    18923    -6     

see 24 files with indirect coverage changes

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