Parser: Properly detect locals that shadow Action View helpers

[marcoroth]

Follow up on #1900.

#1900 taught the action_view_helpers transform to leave block arguments alone, so <%= tag.name %> inside <% @tags.each do |tag| %> stopped turning into a <name> element. It only covered block arguments though, and every other way of binding a local still shadowed nothing:

<% tag = Tag.new(name: "Name") %>

<li><%= tag.name %></li>

The tag.name call was still analyzed as the Action View tag builder, which surfaced through the html-no-unknown-tag linter rule as:

Unknown HTML tag `<name>`. This is not a standard HTML element.

This pull request resolves helper shadowing against a single Prism parse of the whole template instead of tracking scopes by hand.

Related #1762

[github-actions]

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commit: 734f97d