refactor: deprecate polyfillDynamicImport

[patak-dev]

Description

After #3885, users that want to target browsers that don't support dynamic import should use plugin-legacy. polyfillDynamicImport can now be deprecated in Vite core.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

[Shinigami92]

You removed very much from the code 🤔
But is this really a deprecation or just a "breaking change"? If so we can even remove the deprecation comment and just make it clearly visible in the changelogs

... Or in another PR I saw that we have something like a warning printer for logging a deprecation message out

[patak-dev]

You removed very much from the code 🤔
But is this really a deprecation or just a "breaking change"? If so we can even remove the deprecation comment and just make it clearly visible in the changelogs

We should still have the option even when removing it, I'm following the same pattern that Evan used in #4371

... Or in another PR I saw that we have something like a warning printer for logging a deprecation message out

Yup, good catch. Added the runtime deprecation hints