Linter: Only classify an ERB tag's own calls in html-no-nested-forms

[viktorianer]

Fixes #2708
Fixes #2709

html-no-nested-forms collects form helper calls from an ERB tag's Prism node. For a tag that opens a block, that node is the whole call including its block, so the collector also walked into the calls of the tags nested inside the block. Any block helper wrapping a form helper was then classified as a form itself, and the real form helper inside it was reported as nested:

<%= panel do %>
  <%= form_with url: "/search" do |form| %>
    <%= form.submit %>
  <% end %>
<% end %>

The collector now ignores calls that start after the tag's own content (node.content.range.to, a byte offset like Prism's startOffset). A nested tag's calls are judged when the visitor reaches that tag, and a form helper in an inline block inside the same tag is still found.

New cases cover every shape from the issue: a block helper with and without a receiver, nested block helpers, a component render block, a component slot block (#2709), and two form helpers inside a partial render block. Controls keep a real button_to inside form_with inside a block helper, a block helper inside a <form> element, and a button_to in an inline block inside form_with reported.

[marcoroth]

Thanks @viktorianer, looks like this overlapped with #2774. Sorry.

But I merged in main to make sure to keep the tests from this pull request, thank you! 🙏🏼

[viktorianer]

Oh, you found the same issue a bit later? 👌🏼