[FEATURE REQUEST] pkg.installed test mode should show installable version

[nicholasmhughes]

Describe the solution you'd like
Currently, pkg.installed will only show installed as the version for new package installs when run in test mode.

local:
----------
          ID: things
    Function: pkg.installed
      Result: None
     Comment: The following packages would be installed/updated: unzip
     Started: 18:06:05.586891
    Duration: 21196.532 ms
     Changes:   
              ----------
              unzip:
                  ----------
                  new:
                      installed
                  old:

Summary for local
------------
Succeeded: 1 (unchanged=1, changed=1)
Failed:    0
------------
Total states run:     1
Total run time:  21.197 s

It would be helpful if the state showed the intended version to install in test mode.

local:
----------
          ID: things
    Function: pkg.installed
      Result: None
     Comment: The following packages would be installed/updated: unzip
     Started: 18:12:55.880310
    Duration: 774.975 ms
     Changes:   
              ----------
              unzip:
                  ----------
                  new:
                      6.0-23+deb10u3
                  old:

Summary for local
------------
Succeeded: 1 (unchanged=1, changed=1)
Failed:    0
------------
Total states run:     1
Total run time: 774.975 ms

Please Note
If this feature request would be considered a substantial change or addition, this should go through a SEP process here https://github.com/saltstack/salt-enhancement-proposals, instead of a feature request.