PR: Make validation of blocks with Outline explorer data faster

[impact27]

Description of Changes

• 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)

Refactor is_valid for performance

5.x:

>>> spy.window.editor.new()
>>> spy.window.editor.get_current_editor().set_text("#%%\nprint(0)\n"*1000)
>>> import timeit
>>> timeit.timeit("spy.window.editor.run_cell_and_advance()", number=1000, globals={"spy":spy})
7.448802667999999

this PR:

>>> spy.window.editor.new()
>>> spy.window.editor.get_current_editor().set_text("#%%\nprint(0)\n"*1000)
>>> timeit.timeit("spy.window.editor.run_cell_and_advance()", number=1000, globals={"spy":spy})
4.625459233000015

60% faster to run cell and advance

Issue(s) Resolved

Fixes #

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:

[impact27]

The cells were just tested for validity, no need to do it twice

[ccordoba12]

Looks good to me, thanks @impact27!