uv pip uninstall <pkg> against a legacy .egg-info distribution with an empty top_level.txt could resolve "" back to the distribution location itself and end up deleting site-packages.

In uninstall_egg crate, each line from top_level.txt is now trimmed and empty entries are skipped before iterating. Applied the same trim + non-empty handling to namespace_packages.txt so both files are parsed consistently. I did not also change is_path_in_scheme to reject paths equal to a scheme root, since that is a broader defense-in-depth change and outside the scope of this fix.

Covered by test_uninstall_egg_info_empty_top_level next to the existing test_uninstall_egg_info_path_traversal, plus test_uninstall_egg_info_blank_lines_in_top_level for blank and whitespace-only lines between valid entries, which hits the same wipe path before the fix. It fails on main with uninstall must not remove site-packages itself and passes with this fix. Existing uninstall_egg_info, dry_run_uninstall_egg_info, and uninstall_legacy_editable integration tests still pass.

Closes #19113.