[BUG] Windows environ.setenv is not passed to cmd.run spawned processes

Description
Windows doesn't pass the current minion environment to any spawned processes using cmd._run
It is instead using a copy of the environment set in nt.env, which is not updated if the minion updates: https://github.com/saltstack/salt/blob/998c382f5f2c3b4cbf7d96aa6913ada6993909b3/salt/modules/cmdmod.py#L601-L604

Either environ.setenv/setval need to update the nt.environ hash (if possible?), or cmd.run needs to build a correct copy of the env before spawning processes, somehow.

Using permanent or update_minion will not work around this issue, they only fix subsequent runs of the state.

Setup
testenv.sls:

set env:
  environ.setenv:
    - name: TEST_ENV_VAR
    - value: hello there
{%if grains['os'] == 'Windows'%}
spawn a windows test:
  cmd.run:
    - name: $env:TEST_ENV_VAR -eq "hello there"
    - shell: powershell
{%else%}
spawn a linux test:
  cmd.run:
    - name: >-
        [[ $TEST_ENV_VAR == "hello there" ]]
{%endif%}

Steps to Reproduce the behavior
salt '*' state.apply testenv

It will work as expected on linux, windows will not have the env var in the shell and returns False

Expected behavior
Both windows and linux shells have the environment variable set.

Start with salt/modules/cmdmod.py around lines 601-604 and trace how cmd.run/cmd._run prepares the Windows environment for spawned processes. Compare that path with environ.setenv and the provided testenv.sls reproduction; done means the Windows PowerShell command receives TEST_ENV_VAR=hello there in the same state run as the Linux command.