fixrule(input_haspopup_conflict): Add additional checks and update the messages

[shunguoy]

• New or modified help files: input_haspopup_conflict
• Rule bug: input_haspopup_conflict

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

Fixes: #1622
Fixes: #1915 Hellp

Testing reference:

test case: test/v2/checker/accessibility/rules/input_haspopup_conflict_ruleunit/input_list_other.html
After the fix two new violations appear:
"The list attribute for the element is invalid"
"The list attribute for the element does not reference a datalist element"

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.

[ErickRenteria]

Validated