Kite support migration issues

[dalthviz]

• Enabling/disabling action not affecting the status bar (if you had already Kite installed seems like)

After unchecking the enable kite config (and after restarting Spyder) I still see the Kite logo and base text in the status bar:

Enabling/disabling Kite:

Originally posted by @dalthviz in #14314 (comment)

• Seems like the status bar is always showing the Kite: Initializing message and checking the copilot Kite says that was unable to detect Spyder installed (if you had already Kite installed seems like):
  

Also, probably the screenshot available in the Kite help page should be updated to add the new preferences layout in Spyder 5

• After installation (uninstalling Kite and resetting Spyder preferences first) I didn't see the on bording message appearing
• I was unable to trigger the call-to-action after checking the option in the preferences (I had to restart Spyder first)
• Clicking the Learn more button in the call-to-action ends up throwing an exception:

Traceback (most recent call last):
  File "C:\Users\Daniel\Documents\Spyder\spyder\spyder\plugins\completion\providers\kite\widgets\calltoaction.py", line 135, in _learn_more
    kite = self.parent().completions.get_client('kite')
AttributeError: 'CompletionPlugin' object has no attribute 'get_client'

Just in case, I did all of this testing on Windows and to trigger the call-to-action I used this code:

import matplotlib.pyplot as plt
fig = plt.figure()
fig.add