feat(DRAFT): reintroduce adder tests

[manuel3108]

This reintroduces the adder tests previously in svelte-add, now with significant enhancements:

• "End to End" tests, as they were known, are those we had before. They install all dependencies, run the development server, and perform checks using playwright.
• "Snapshot" tests run the adders across various project types, collect all the changed files, and create snapshots, but only from the changed files (to be committed to git).

Notes:

• Snapshots are excluded from this PR for clarity. They should be re-added before or after merging, typically found in packages\adder-tests\_snapshots and community-adder-template\_snapshot, mirroring the structure of the test output directories.
• The peculiar passing around of vitest functions (refer to: https://github.com/sveltejs/cli/blob/1532153aa16f164bb0d67ef735b2a099e8424bb6/packages/adder-tests/tests/official/end2end.ts) is intentional. The goal is to keep @svelte-cli/adder-testing-library as a standalone package for npm, aiding community adders. Thus, incorporating our test execution within @svelte-cli/adder-testing-library isn't viable. Moreover, vitest doesn't recognize tests within the current package if they're in node_modules.
• New beforeAll and beforeEach test hooks have been introduced, along with their counterparts for after. This allows, for example, the drizzle adder to manage docker containers independently.

Remaining tasks:

• Resolve an issue with eslint, which is producing an unclear error message.
• Address vitest concerns, particularly regarding snapshots. (they probably arise because the snapshot files are not present. They are created locally on the fly, but probably not in CI)

Future enhancements (beyond the scope of this update):

• Introduce a new project test type called "demo," which applies the project to our demo template via the CLI. This could be beneficial for non-clean projects.
• Implement sanity tests for community adders: Check if the npm package exists, if the repository exists, and if it's compatible with the latest major version of sv, among other checks.
• For adders that do not offer custom tests, we should at least apply the adder and execute the build command to ensure it hasn't caused any disruptions.
• Explore methods to expedite the application of the storybook adder. Currently, applying the storybook adder to five different projects takes approximately 1.5 minutes, accounting for about 25% of the total test time.

[pkg-pr-new]

Open in Stackblitz

pnpm add https://pkg.pr.new/sveltejs/cli/sv@32

commit: ff96d27

[manuel3108]

Note the change in #76 may require some additional checks here

[manuel3108]

This will require rather dramatic rebasing some time after summit

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[manuel3108]

Closing in favor of #275