Update within_testid and find_by_testid helper to include context

What does this MR do and why?

Update dom_helpers to allow passing in a context to allow something like:

my_scope = page.find("selector")
within(my_scope) do
    find_by_testid('my_button').click
end

To something like this:

my_scope = page.find("selector")
find_by_testid('my_button', context: my_scope).click

This is the original intent of #433496 (closed). This MR also marks violations related to be_axe_clean as todo, since we have to explore other ways to fix them.

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Related to #433496 (closed)