std: refactor test-runner to no longer require tests to be exported (#9355)

# Description
Test runner now performs following actions in order to run tests:
* Module file is opened
* Public function with random name is added to the source code, this
function calls user-specified private function
* Modified module file is saved under random name in $nu.temp-path
* Modified module file is imported in subprocess, injected function is
called by the test runner
# User-Facing Changes
<!-- List of all changes that impact the user experience here. This
helps us keep track of breaking changes. -->
* Test functions no longer need to be exported
* test functions no longer need to reside in separate test_ files
* setup and teardown renamed to before-each and after-each respectively
* before-all and after-all functions added that run before all tests in
given module. This matches the behavior of test runners used by other
languages such as JUnit/TestNG or Mocha
# Tests + Formatting

# After Submitting

---------

Co-authored-by: Kamil <skelly37@protonmail.com>
Co-authored-by: amtoine <stevan.antoine@gmail.com>

crates/nu-std/tests/logger_tests/test_basic_commands.nu

@@ -42,47 +42,47 @@ def "assert message short" [
     assert str contains $output "test message"
 }
 
-export def test_critical [] {
+def test_critical [] {
     assert no message 99 critical
     assert message CRITICAL critical CRT
 }
 
-export def test_critical_short [] {
+def test_critical_short [] {
     assert message short CRITICAL critical C
 }
 
-export def test_error [] {
-    assert no message CRITICAL error 
+def test_error [] {
+    assert no message CRITICAL error
     assert message ERROR error ERR
 }
 
-export def test_error_short [] {
+def test_error_short [] {
     assert message short ERROR error E
 }
 
-export def test_warning [] {
-    assert no message ERROR warning 
+def test_warning [] {
+    assert no message ERROR warning
     assert message WARNING warning WRN
 }
 
-export def test_warning_short [] {
+def test_warning_short [] {
     assert message short WARNING warning W
 }
 
-export def test_info [] {
-    assert no message WARNING info 
+def test_info [] {
+    assert no message WARNING info
     assert message INFO info "INF" # INF has to be quoted, otherwise it is the `inf` float
 }
 
-export def test_info_short [] {
+def test_info_short [] {
     assert message short INFO info I
 }
 
-export def test_debug [] {
-    assert no message INFO debug 
+def test_debug [] {
+    assert no message INFO debug
     assert message DEBUG debug DBG
 }
 
-export def test_debug_short [] {
+def test_debug_short [] {
     assert message short DEBUG debug D
-}
+}