feat: Adding Delete file command

[czp13]

Description

Adding delete file handler, needed for copilot (ext) project to be able to handle cases when we want to undo cases where we added a new file.

Type of change

• Bugfix
• Feature

Checklist

• I have read the contribution guide: https://vaadin.com/docs/latest/guide/contributing/overview/
• I have added a description following the guideline.
• The issue is created in the corresponding repository and I have referenced it.
• I have added tests to ensure my change is effective and works as intended.
• New and existing tests are passing locally with my change.
• I have performed self-review and corrected misspellings.

Additional for Feature type of change

• Enhancement / new feature was discussed in a corresponding GitHub issue and Acceptance Criteria were created.

[czp13]

I am not sure if we want to add tests for covering these handlers, I saw only one test so far called:

• CopilotUndoManagerTest.

[MarcinVaadin]

Works fine, tested with undo. Redo after undo needs to be investigated in separate PR.

[github-actions]

Artifact build on last commit: distributions.zip.
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[github-actions]

Plugin com.vaadin.intellij-plugin:1.0-SNAPSHOT against IC-233.11799.241

Compatible. 1 usage of deprecated API. 53 usages of experimental API

[github-actions]

Plugin com.vaadin.intellij-plugin:1.0-SNAPSHOT against IC-251.14649.49

Compatible. 2 usages of deprecated API. 25 usages of experimental API

[github-actions]

Plugin com.vaadin.intellij-plugin:1.0-SNAPSHOT against IU-251.14649.49

Compatible. 2 usages of deprecated API. 37 usages of experimental API

[github-actions]

Plugin com.vaadin.intellij-plugin:1.0-SNAPSHOT against IU-233.11799.241

Compatible. 1 usage of deprecated API. 65 usages of experimental API

[MarcinVaadin]

I am not sure if we want to add tests for covering these handlers

It's pretty complicated to add tests for Java based projects. Needs some investigation about how to setup project with JVM and proper dependencies.