PR: Fix errors when getting Matplotlib backend in the kernel (IPython console)

[ccordoba12]

Description of Changes

• Issue Kernel is dead message when starting Spyder #22179 was caused because the kernel was not detected as alive after it starts in slow systems (i.e. those in which the kernel takes too long to start).
• Issue CommError upon opening existing console #22194 was a simple CommError when getting when the backend if the comm is not connected.
• Fix test_restart_interactive_backend on Windows. That allows to check if the MatplotlibStatus widget is working fine on it.
• Use functools.partial instead of lambda for the anonymous slots used in MatplotlibStatus. That's necessary because lambda slots prevent garbage collecting PyQt objects when self is used in them. However, functools.partial ones don't have that problem.

Issue(s) Resolved

Fixes #22194.
Fixes #22179.

Affirmation

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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: @ccordoba12

[ccordoba12]

@dalthviz, this is ready for review.

[dalthviz]

Thanks @ccordoba12 ! Checked locally and seems like things are working as expected 👍