fix(resolve): use different importer check for css imports

[bluwy]

Description

This should fix the ecosystem CI failures using the vue jsx plugin. Alternative fix for #12796.

Previously, the checking method would convert basedir of /__vue-jsx-ssr-register-helper to /, which would always exist, causing issues. I've changed to check the trailing * specifically from CSS processing to handle the issue in the linked PR above instead.

CSS processing appends * because the tooling only provides the importer directory for resolving, which is an issue for the resolver as it expects a file.

I initially tried to avoid this, but I don't think there's another safer way besides hardcoding it.

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the PR Title Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

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[patak-dev]

/ecosystem-ci run

[vite-ecosystem-ci]

📝 Ran ecosystem CI: Open

suite	result
astro	✅ success
histoire	❌ failure
iles	❌ failure
ladle	✅ success
laravel	✅ success
marko	✅ success
nuxt	❌ failure
previewjs	✅ success
qwik	✅ success
rakkas	✅ success
sveltekit	✅ success
vite-plugin-ssr	undefined null
vite-plugin-react	✅ success
vite-plugin-react-pages	✅ success
vite-plugin-react-swc	✅ success
vite-plugin-svelte	✅ success
vite-plugin-vue	✅ success
vite-setup-catalogue	✅ success
vitepress	✅ success
vitest	✅ success
windicss	✅ success