Add error for case/when on same line in ERB tag

[tvararu]

This adds test cases and a custom error to handle code like:

<% case variable when "a" %>
  A
<% when "b" %>
  B
<% else %>
  C
<% end %>

<% case value in 1 %>
  One
<% in 2 %>
  Two
<% end %>

While this is valid ERB, it poses issues for the parser, as it would mean we'd need to turn a single statement into multiple nodes.

Those same blocks can be rewritten as:

<% case variable %>
<% when "a" %>
  A
<% when "b" %>
  B
<% else %>
  C
<% end %>

<% case value %>
<% in 1 %>
  One
<% in 2 %>
  Two
<% end %>

Which is unambiguous to parse, and arguably more legible.

This adds a new ERBCaseWithConditionsInTagError to detect this pattern and direct users to split into separate tags.

[tvararu]

@marcoroth I tried approaching this in a different way, like:

if ((analyzed->case_node_count > 0 && analyzed->when_node_count > 0) ||
    (analyzed->case_match_node_count > 0 && analyzed->in_node_count > 0)) {
  append_erb_case_with_conditions_error(
    erb_content_node->base.location.start,
    erb_content_node->base.location.end,
    erb_content_node->base.errors
  );
}

But it doesn't look like case x when "a" increments the when_node_count, it stays 0...

We have to add something to src/analyzed_ruby.c as the analyzed struct doesn't store enough information for us to infer whether a case node has inline conditionals; case_node->conditions.size is what we need but we need to extract it somewhere...

We could have analyzed->inline_conditionals_count, that would be an int instead of a boolean so it's more consistent with the rest of the struct. I pushed up a new commit with this but it's very similar to the boolean one, I've also changed the error name and the message

If you like this approach better I can rebase and squash the commits 👍