fix: avoid dashmap deadlock for correlated queries

[xushiyan]

Description

• Use include_str! to embed Avro schema files at compile time instead of runtime file I/O in delete.rs
• Use read locks instead of write locks on DashMap in fs_view::collect_file_slices to avoid potential deadlocks during correlated queries; metadata loading is deferred to owned clones after locks are released

How are the changes test-covered

• N/A
• Automated tests (unit and/or integration tests)
• Manual tests
  • Details are described below

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.92%. Comparing base (29188ad) to head (742e165).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #539      +/-   ##
==========================================
+ Coverage   84.91%   84.92%   +0.01%     
==========================================
  Files          73       73              
  Lines        4606     4597       -9     
==========================================
- Hits         3911     3904       -7     
+ Misses        695      693       -2     

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