Fix dirs removal warning (#14029)

# Description

* Primary purpose is to fix an issue with a missing escaped opening
parenthesis in the warning message when running an old `dirs` alias.
This was creating an error condition from improper interpolation.

Also

* Incorporates #13842 feedback from @kubouch by renaming `std/lib` to
`std/util`
* Removes duplication of code in `export-env`
* Renames submodule exports to `std/<submodule>` rather than
`./<submodule>` - No user-facing change other than `view files` appears
"prettier".
* In #13842, I converted the test cases to use `use std/<module>`
syntax. Previously, the tests were (effectively) using `use std *` (due
to pre-existing bugs, now fixed).

So "before", we only had test coverage on `use std *`, and "after" we
only had test coverage on `use std/<module>`. I've started adding test
cases so that we have coverage on *both* scenarios going forward.

For now, `formats` and `util` have been updated with tests for both
scenarios. I'll continue adding the others in future PRs.

# User-Facing Changes

No user-facing changes - Bug fix, refactor, and test cases only

# Tests + Formatting

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

# After Submitting

Still working on updating the Doc. I ran into the `dirs` issue while
writing it and rabbit-trailed to fix it in this PR.

crates/nu-std/tests/test_formats.nu

@@ -1,4 +1,6 @@
+# Test std/formats when importing module-only
 use std/assert
+use std/formats *
 
 def test_data_multiline [] {
   let lines = [
@@ -19,7 +21,6 @@ def test_data_multiline [] {
 
 #[test]
 def from_ndjson_multiple_objects [] {
-  use std/formats *
   let result = test_data_multiline | from ndjson
   let expect = [{a:1},{a:2},{a:3},{a:4},{a:5},{a:6}]
   assert equal $result $expect "could not convert from NDJSON"
@@ -27,7 +28,6 @@ def from_ndjson_multiple_objects [] {
 
 #[test]
 def from_ndjson_single_object [] {
-  use std/formats *
   let result = '{"a": 1}' | from ndjson
   let expect = [{a:1}]
   assert equal $result $expect "could not convert from NDJSON"
@@ -35,13 +35,11 @@ def from_ndjson_single_object [] {
 
 #[test]
 def from_ndjson_invalid_object [] {
-  use std/formats *
   assert error { '{"a":1' | from ndjson }
 }
 
 #[test]
 def from_jsonl_multiple_objects [] {
-  use std/formats *
   let result = test_data_multiline | from jsonl
   let expect = [{a:1},{a:2},{a:3},{a:4},{a:5},{a:6}]
   assert equal $result $expect "could not convert from JSONL"
@@ -49,7 +47,6 @@ def from_jsonl_multiple_objects [] {
 
 #[test]
 def from_jsonl_single_object [] {
-  use std/formats *
   let result = '{"a": 1}' | from jsonl
   let expect = [{a:1}]
   assert equal $result $expect "could not convert from JSONL"
@@ -57,13 +54,11 @@ def from_jsonl_single_object [] {
 
 #[test]
 def from_jsonl_invalid_object [] {
-  use std/formats *
   assert error { '{"a":1' | from jsonl }
 }
 
 #[test]
 def to_ndjson_multiple_objects [] {
-  use std/formats *
   let result = [{a:1},{a:2},{a:3},{a:4},{a:5},{a:6}] | to ndjson | str trim
   let expect = test_data_multiline
   assert equal $result $expect "could not convert to NDJSON"
@@ -71,7 +66,6 @@ def to_ndjson_multiple_objects [] {
 
 #[test]
 def to_ndjson_single_object [] {
-  use std/formats *
   let result = [{a:1}] | to ndjson | str trim
   let expect = "{\"a\":1}"
   assert equal $result $expect "could not convert to NDJSON"
@@ -79,7 +73,6 @@ def to_ndjson_single_object [] {
 
 #[test]
 def to_jsonl_multiple_objects [] {
-  use std/formats *
   let result = [{a:1},{a:2},{a:3},{a:4},{a:5},{a:6}] | to jsonl | str trim
   let expect = test_data_multiline
   assert equal $result $expect "could not convert to JSONL"
@@ -87,7 +80,6 @@ def to_jsonl_multiple_objects [] {
 
 #[test]
 def to_jsonl_single_object [] {
-  use std/formats *
   let result = [{a:1}] | to jsonl | str trim
   let expect = "{\"a\":1}"
   assert equal $result $expect "could not convert to JSONL"