fixrule(element_scrollable_tabbable, element_tabbable_role_valid): Fix issues related to scrollable and tabbable elements

[shunguoy]

• Rule bug: element_scrollable_tabbable, element_tabbable_role_valid

This PR is related to the following issue(s):

• Fixes Color contrast issue with a label that is associated with a disabled button  #1918
• Fixes [Rule_Bug]: The tabbable element’s role ‘region’ is not a widget role  #2054
• Fixes The rule "element_tabbable_role_valid" only partially skips the elements with CSS overflow #2159

Testing reference:

• test case: test/v2/checker/accessibility/rules/element_scrollable_tabbable_ruleunit/scrollable_element_tabbable.html
  before the fix: an error reported on the first section element: "The tabbable element does not have a valid widget role".
  After the fix: the error goes away from the first section element. However, a different error is reported on the second and third section elements: "The tabbable element does not have a valid widget role".

I have conducted the following for this PR:

• I validated this code in Chrome and FF
• I validated this fix in my local env
• I provided details for testing
• This PR has been reviewed and is ready for test
• I understand that the title of this PR will be used for the next release notes.

Assets to aide review attached

• Links to design artifacts
• Links to video walkthrough of user experience
• Other

Definition of Done

• Peer review complete
• Secondary review complete
• Staging deployment verified