clang: Disable source order sorting for now. (#2558)

* clang: Clean up source order sorting.

This doesn't change behavior but is easier to debug and reason about
(because you have the relevant cursors there).

* clang: Disable source order sorting for now.

This disables (hopefully temporarily) source order sorting, for causing
correctness regressions like #2556.

Fixes #2556.

* tests: Add a test for #2556

* Remove merge artifact

* Update clang.rs

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Co-authored-by: Christian Poveda Ruiz <31802960+pvdrz@users.noreply.github.com>

Author: emilio