refactor(tvix/eval) s/NixPath/NixSearchPath/

Since NixString is the Rust type for nix strings, people might
mistake NixPath for the Rust type of nix paths, which it is not.
Let's call it NixSearchPath instead.

Signed-off-by: Adam Joseph <adam@westernsemico.com>
Change-Id: Ib2ea155c4b27cb90d6180a04ea7b951d86607373
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6927
Reviewed-by: kanepyork <rikingcoding@gmail.com>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

tvix/eval/src/lib.rs

@@ -12,7 +12,7 @@ mod value;
 mod vm;
 mod warnings;
 
-mod nix_path;
+mod nix_search_path;
 #[cfg(test)]
 mod properties;
 #[cfg(test)]