Merged tests to produce a single binary (#12826)

This PR should close #7147 

# Description
Merged src/tests into /tests to produce a single binary.

![image](https://github.com/nushell/nushell/assets/94604837/84726469-d447-4619-b6d1-2d1415d0f42e)

# User-Facing Changes
No user facing changes

# Tests + Formatting
Moved tests. Tollkit check pr pass.

# After Submitting

---------

Co-authored-by: Ian Manske <ian.manske@pm.me>

tests/main.rs

@@ -11,5 +11,6 @@ mod path;
 mod plugin_persistence;
 #[cfg(feature = "plugin")]
 mod plugins;
+mod repl;
 mod scope;
 mod shell;