PR: Correctly handle the option to run in a dedicated console without clearing variables

[bcolsen]

Description of Changes

Added the option to run in a dedicated console without clearing variables. I forgot to make a branch in #19984 so I'm replacing it with this one.

• Wrote at least one-line docstrings (for any new functions)
• Added unit test(s) covering the changes (if testable)

• Included a screenshot or animation (if affecting the UI, see Licecap)

Added the option to run in a dedicated console without clearing variables because it seems like that should be an option and I like my interactive plot windows to stay in place and not pop up all the time

Issue(s) Resolved

Fixes #19983

Affirmation

By submitting this Pull Request or typing my (user)name below,
I affirm the Developer Certificate of Origin
with respect to all commits and content included in this PR,
and understand I am releasing the same under Spyder's MIT (Expat) license.

I certify the above statement is true and correct: bcolsen

[dalthviz]

Thanks @bcolsen for the help with this! Left a suggestion for the comment on the new case added to the tests when changing the clear_namespace config.

Other than that this LGTM 👍

[ccordoba12]

Thanks @bcolsen!

Note: The failure in our tests is unrelated to this.