fix(hooks): updating $env.config now correctly updates config state. (#16021)

- fixes #14946

- related #15227
- > [When I run nushell with the hook, the hook itself works as
expected, correctly detects system theme and changes
$env.config.color_config. However, it seems that the change to
$env.config.color_config is not propagated outside the
hook](https://github.com/nushell/nushell/issues/15227#issuecomment-2695287318)
- > [But it suffers from the same problem - modifications made to the
$env.config variable are not visible outside of the hook (which I'm not
sure if is correct behavior or
bug).](https://github.com/nushell/nushell/issues/15227#issuecomment-2695741542)
- > [I also managed to get it working with def --env, but there was one
more issue, I had to change $env.config.hooks.pre_prompt = [{
switch_theme }] into $env.config.hooks.pre_execution = ([ switch_theme
])](https://github.com/nushell/nushell/issues/15227#issuecomment-2704537565)
(having to use a string hook rather than a closure)

- related #11082
  > Might be possible solve or at least mitigate using a similar method

# Description

Recently realized that changes made to `$env.config` in closure hooks
don't take effect whereas string hooks don't have that problem.

After some investigation:
- Hooks' environment was not preserved prior to #5982 >
[2309601](2309601dd4/crates/nu-cli/src/repl.rs (L823-L840))
- `redirect_env` which properly updates the config state was implemented
afterwards in #6355 >
[ea8b0e8](ea8b0e8a1d/crates/nu-engine/src/eval.rs (L174-L190))

Simply using `nu_engine::eval::redirect_env` for the environment update
was enough to fix the issue.

# User-Facing Changes
Hooks can update `$env.config` and the configuration change will work as
expected.

# Tests + Formatting

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

# After Submitting
N/A

Co-authored-by: Bahex <17417311+Bahex@users.noreply.github.com>

crates/nu-cmd-base/src/hook.rs

@@ -1,5 +1,5 @@
 use miette::Result;
-use nu_engine::{eval_block, eval_block_with_early_return};
+use nu_engine::{eval_block, eval_block_with_early_return, redirect_env};
 use nu_parser::parse;
 use nu_protocol::{
     PipelineData, PositionalArg, ShellError, Span, Type, Value, VarId,
@@ -325,19 +325,7 @@ fn run_hook(
     }
 
     // If all went fine, preserve the environment of the called block
-    let caller_env_vars = stack.get_env_var_names(engine_state);
+    redirect_env(engine_state, stack, &callee_stack);
 
-    // remove env vars that are present in the caller but not in the callee
-    // (the callee hid them)
-    for var in caller_env_vars.iter() {
-        if !callee_stack.has_env_var(engine_state, var) {
-            stack.remove_env_var(engine_state, var);
-        }
-    }
-
-    // add new env vars from callee to caller
-    for (var, value) in callee_stack.get_stack_env_vars() {
-        stack.add_env_var(var, value);
-    }
     Ok(pipeline_data)
 }