[Enhancement] Redesign Set Global/Suite/Test Variable and VAR Statement handling

[zastress]

Describe the bug Global Variables that are declared inside Test Setup or Suite Setup are not recognized inside a test case

If possible add some example source code like:

*** Settings ***
Test Setup    My Test Keyword

*** Keywords ***

My Test Keyword
    VAR    ${global}    scope=GLOBAL

*** Test Cases ***
Example Test Case
    Log    ${global}

Expected behavior Variable should not be marked inside test as non-existent