Analysis: Collect what state a template depends on

[marcoroth]

This pull request adds the per-template half of dependency tracking, which is reading a template to find out what it depends on.

collectTemplateDependencies answers, for one template, which instance variables and constants it reads, which locals it declares and receives, which templates it renders and with what, and which calls are helpers as opposed to names nobody has accounted for.

collectTemplateDependencies(Herb, "app/views/posts/show.html.erb", source)
// {
//   instanceVariables: ["@post"],
//   constants: ["Current.user"],
//   localsDeclared: [],
//   localsReceived: { title: "@post.title" },
//   renderCalls: [{ partial: "shared/header", locals: { title: "@post.title" } }],
//   helperCalls: ["link_to", "render"],
//   unknownCalls: ["current_user"],
// }

This is the input to working out what a change invalidates. On its own it also answers questions the linter already asks in more roundabout ways.

Follow up on #1667

[github-actions]

🌿 Interactive Playground and Documentation Preview

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_{🌱 Grown from commit 2c2f589}

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✅ Preview deployment has been cleaned up.

[pkg-pr-new]

npx https://pkg.pr.new/@herb-tools/formatter@2187

npx https://pkg.pr.new/@herb-tools/language-server@2187

npx https://pkg.pr.new/@herb-tools/linter@2187

commit: 2c2f589