refactor(vue): only ship es modules

[liamdebeasi]

Re-landing #26043 because I forgot to set the commit message.

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
  • Some docs updates need to be made in the ionic-docs repo, in a separate PR. See the contributing guide for details.
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue URL: resolves #25104

Prior to the Custom Elements Bundle switch, Ionic Core shipped as CommonJS. Ionic Vue shipped CommonJS and ES Module entrypoints that consumed Ionic Core.

With the switch to Custom Element Bundle, Ionic Vue only consumed the ES Module version of Ionic Core. As a result, the CommonJS entry point was no longer needed. This caused issues with Vitest where tests would not run (see linked issue).

What is the new behavior?

• Ionic Vue no longer ships a CommonJS entry point.
  Note: This likely will not cause issues with developer applications. If their environment did not support ES Modules, then they would already have been running into issues due to Ionic Core being ES Modules. However, I do think this should be treated as a breaking change just to be safe.

Does this introduce a breaking change?

• Yes
• No

Other information