[master] Add pkg.installed show installable version in test mode

[nicholasmhughes]

What does this PR do?

See issue for details.

What issues does this PR fix or reference?

Fixes: #63985

Previous Behavior

Previously, pkg.installed only showed 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

New Behavior

Now the state shows 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

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

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Yes

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