[Unified Compiler] Renaming python_compiler into unified_compiler

[PietropaoloFrisoni]

This PR should be merged along with this PR in Catalyst

Context: This PR changes name from python.compiler into unified.compiler and updates all the entries in the source code.

Description of the Change: As above.

Benefits: Better name.

Possible Drawbacks: None that I can think of.

Related GitHub Issues: None.

[sc-98172]

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit doc/releases/changelog-dev.md with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.

[JerryChen97]

oh no seems most of the tests in external tests pack still use the old API

[PietropaoloFrisoni]

oh no seems most of the tests in external tests pack still use the old API

This is because we need to update Catalyst as well (we get failures when we import getXDSLPluginAbsolutePath)

[isaacdevlugt]

I don't see unified_compiler in the qml.compiler API 🤔 (here: https://xanaduai-pennylane--8121.com.readthedocs.build/en/8121/code/qml_compiler.html). Is it purposefully hidden?

[PietropaoloFrisoni]

Thanks Isaac. We can add a section describing the unified_compiler module in the pennylane/compiler/__init__.py file, and it should be displayed in the doc. Now there is an entry describing the Compiler module only. Please let me know what you think, although I assume that you would like Product to take care of this (tagging also @josh146 for visibility)

[isaacdevlugt]

Based on conversations in-person, we decided to name this module compiler.interface. We may choose to revisit this in the future when the features become more public.

@PietropaoloFrisoni looks good! I would change the title of the PR—that's it :)

[mudit2812]

Closing, no longer needed.