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/std/deprecated_dirs.nu

@@ -26,7 +26,7 @@ print -e $"
 (ansi red)Warning:(ansi reset) The 'std dirs' module will no longer automatically
 be loaded in the next release. To continue using the Shells
 feature, and to remove this warning, please add the following
-to your startup configuration (typically env.nu or config.nu):
+to your startup configuration \(typically env.nu or config.nu\):
 
 use std/dirs shells-aliases *
 

crates/nu-std/std/mod.nu

@@ -1,24 +1,24 @@
 # std.nu, `used` to load all standard library components
 
 # Top-level commands: ellie, repeat, null-device, and "path add"
-export use lib *
+export use std/util *
 
 # std submodules
-export module ./assert
-export module ./bench
-export module ./dt
-export module ./formats
-export module ./help
-export module ./input
-export module ./iter
-export module ./log
-export module ./math
-export module ./xml
+export module std/assert
+export module std/bench
+export module std/dt
+export module std/formats
+export module std/help
+export module std/input
+export module std/iter
+export module std/log
+export module std/math
+export module std/xml
 
 # Load main dirs command and all subcommands
-export use ./dirs main
-export module ./dirs {
-  export use ./dirs [
+export use std/dirs main
+export module dirs {
+  export use std/dirs [
     add
     drop
     next
@@ -29,11 +29,6 @@ export module ./dirs {
 
 # Workaround for #13403 to load export-env blocks from submodules
 export-env {
-    # log
-    $env.NU_LOG_FORMAT = $env.NU_LOG_FORMAT? | default "%ANSI_START%%DATE%|%LEVEL%|%MSG%%ANSI_STOP%"
-    $env.NU_LOG_DATE_FORMAT = $env.NU_LOG_DATE_FORMAT? | default "%Y-%m-%dT%H:%M:%S%.3f"
-    
-    # dirs
-    $env.DIRS_POSITION = 0
-    $env.DIRS_LIST = [($env.PWD | path expand)]
+    use std/log []
+    use std/dirs []
 }