Add ConfigDirNotFound error (#11849)

<!--
if this PR closes one or more issues, you can automatically link the PR
with
them by using one of the [*linking
keywords*](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword),
e.g.
- this PR should close #xxxx
- fixes #xxxx

you can also mention related issues, PRs or discussions!
-->

# Description
<!--
Thank you for improving Nushell. Please, check our [contributing
guide](../CONTRIBUTING.md) and talk to the core team before making major
changes.

Description of your pull request goes here. **Provide examples and/or
screenshots** if your changes affect the user experience.
-->

Currently, there's multiple places that look for a config directory, and
each of them has different error messages when it can't be found. This
PR makes a `ConfigDirNotFound` error to standardize the error message
for all of these cases.

# User-Facing Changes
<!-- List of all changes that impact the user experience here. This
helps us keep track of breaking changes. -->

Previously, the errors in `create_nu_constant()` would say which config
file Nushell was trying to get when it couldn't find the config
directory. Now it doesn't. However, I think that's fine, given that it
doesn't matter whether it couldn't find the config directory while
looking for `login.nu` or `env.nu`, it only matters that it couldn't
find it.

This is what the error looks like:


![image](https://github.com/nushell/nushell/assets/45539777/52298ed4-f9e9-4900-bb94-1154d389efa7)

# Tests + Formatting
<!--
Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used` to
check that you're using the standard code style
- `cargo test --workspace` to check that all tests pass (on Windows make
sure to [enable developer
mode](https://learn.microsoft.com/en-us/windows/apps/get-started/developer-mode-features-and-debugging))
- `cargo run -- -c "use std testing; testing run-tests --path
crates/nu-std"` to run the tests for the standard library

> **Note**
> from `nushell` you can also use the `toolkit` as follows
> ```bash
> use toolkit.nu # or use an `env_change` hook to activate it
automatically
> toolkit check pr
> ```
-->

# After Submitting
<!-- If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.
-->

---------

Co-authored-by: Antoine Stevan <44101798+amtoine@users.noreply.github.com>

src/tests/test_config_path.rs

@@ -28,32 +28,45 @@ fn test_default_config_path() {
         let _ = fs::create_dir_all(&config_dir_nushell);
     }
     let cwd = std::env::current_dir().expect("Could not get current working directory");
+
+    let config_dir_nushell =
+        std::fs::canonicalize(&config_dir_nushell).expect("canonicalize config dir failed");
+    let actual = nu!(cwd: &cwd, "$nu.default-config-dir");
+    assert_eq!(actual.out, adjust_canonicalization(&config_dir_nushell));
+
     let config_path = config_dir_nushell.join("config.nu");
-
-    // Create an empty file for canonicalization if it doesn't already exist
-    if !config_path.exists() {
-        let _ = std::fs::File::create(&config_path);
-    }
-
     // We use canonicalize here in case the config or env is symlinked since $nu.config-path is returning the canonicalized path in #8653
-    let canon_config_path = adjust_canonicalization(
-        std::fs::canonicalize(config_path).expect("canonicalize config-path failed"),
-    );
-
+    let canon_config_path =
+        adjust_canonicalization(std::fs::canonicalize(&config_path).unwrap_or(config_path));
     let actual = nu!(cwd: &cwd, "$nu.config-path");
     assert_eq!(actual.out, canon_config_path);
+
     let env_path = config_dir_nushell.join("env.nu");
-
-    // Create an empty file for canonicalization if it doesn't already exist
-    if !env_path.exists() {
-        let _ = std::fs::File::create(&env_path);
-    }
-
-    let canon_env_path = adjust_canonicalization(
-        std::fs::canonicalize(env_path).expect("canonicalize of env-path failed"),
-    );
+    let canon_env_path =
+        adjust_canonicalization(std::fs::canonicalize(&env_path).unwrap_or(env_path));
     let actual = nu!(cwd: &cwd, "$nu.env-path");
     assert_eq!(actual.out, canon_env_path);
+
+    let history_path = config_dir_nushell.join("history.txt");
+    let canon_history_path =
+        adjust_canonicalization(std::fs::canonicalize(&history_path).unwrap_or(history_path));
+    let actual = nu!(cwd: &cwd, "$nu.history-path");
+    assert_eq!(actual.out, canon_history_path);
+
+    let login_path = config_dir_nushell.join("login.nu");
+    let canon_login_path =
+        adjust_canonicalization(std::fs::canonicalize(&login_path).unwrap_or(login_path));
+    let actual = nu!(cwd: &cwd, "$nu.loginshell-path");
+    assert_eq!(actual.out, canon_login_path);
+
+    #[cfg(feature = "plugin")]
+    {
+        let plugin_path = config_dir_nushell.join("plugin.nu");
+        let canon_plugin_path =
+            adjust_canonicalization(std::fs::canonicalize(&plugin_path).unwrap_or(plugin_path));
+        let actual = nu!(cwd: &cwd, "$nu.plugin-path");
+        assert_eq!(actual.out, canon_plugin_path);
+    }
 }
 
 #[test]