Angular: Fix CSF Plugin

[valentinpalkovic]

Closes #21387, #17233, #24241, #20475, #14043

What I did

The CSF Plugin was reading the source file from the filesystem instead of processing it as a loader within a loader chain. The transformations applied by the CSF Plugin overrode any processing that had occurred before. Angular for instance does also access the filesystem directly to transform files. The CSF loader therefore has to be applied at a later point. This requires the CSF loader to apply the necessary transformations on already transformed files. The loader has to read the original source file, though, to get the source code before any other transformer touches it (prevent removed comments or transformed code).

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

Test that JSON comments are preserved

1. Go to one of the deployed Angular Storybooks in Chromatic
2. Visit ?path=/docs/addons-docs-docspage-basic--docs story
3. JSON docs are applied as descriptions to args

Storysource

1. Create an Angular sandbox
2. Install @storybook/storysource
3. Visit a Story in the browser. The Storysource section in the controls tab should not show "Loading source...", but the actual source code of that Story instead.

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli/src/sandbox-templates.ts

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>

[shilman]

❤️ ❤️ ❤️
This looks so much better!!!
❤️ ❤️ ❤️