feat(#2682): unphi mojo test packs + bug fixes

[maxonfjvipon]

Closes: #2682
Closes: #2642

What's done:

• Added test packs for UnphiMojo
• Added test that converts phi to xmir and back
• Fixed bugs with explicit data transformation

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PR-Codex overview

This PR focuses on updating the UnphiMojo class in the eo-maven-plugin.

Detailed summary

• The UnphiMojo class in the eo-maven-plugin has been modified.
• The home.save() method has been updated to use a modified PhiSyntax object.
• The phi.getFileName().toString() now replaces the ".phi" extension with an empty string.
• The UnphiMojoTest class has been modified to remove the `@

The following files were skipped due to too many changes: eo-maven-plugin/src/test/java/org/eolang/maven/UnphiMojoTest.java

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[maxonfjvipon]

@yegor256 please have a look

[yegor256]

@rultor merge

[rultor]

@rultor merge

@yegor256 OK, I'll try to merge now. You can check the progress of the merge here

[rultor]

@rultor merge

@yegor256 Done! FYI, the full log is here (took me 18min)