Removes export env command (#6468)

* remove export_env command

* remove several export env usage in test code

* adjust hiding relative test case

* fix clippy

* adjust tests

* update tests

* unignore these tests to expose ut failed

* using `use` instead of `overlay use` in some tests

* Revert "using `use` instead of `overlay use` in some tests"

This reverts commit 2ae24b24c3.

* Revert "adjust hiding relative test case"

This reverts commit 4369af6d05.

* Bring back module example

* Revert "update tests"

This reverts commit 6ae94ef513.

* Fix tests

* "Fix" a test

* Remove remaining deprecated env functionality

* Re-enable environment hiding for `hide`

To not break virtualenv since the overlay update is not merged yet

* Fix hiding env in `hide` and ignore some tests

Co-authored-by: kubouch <kubouch@gmail.com>

crates/nu-command/src/default_context.rs

@@ -42,7 +42,6 @@ pub fn create_default_context() -> EngineState {
             ExportCommand,
             ExportDef,
             ExportDefEnv,
-            ExportEnvModule,
             ExportExtern,
             ExportUse,
             Extern,