⚡ only build bindings target for Python package (#643)

## Description

This PR slighlty optimizes the build times for the Python package by
only building the `_core` bindings target. This avoid compiling targets
that will never make it into the final wheel.

## Checklist:

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- [x] The pull request only contains commits that are related to it.
- [x] I have added appropriate tests and documentation.
- [x] I have made sure that all CI jobs on GitHub pass.
- [x] The pull request introduces no new warnings and follows the
project's style guidelines.

Signed-off-by: burgholzer <[email protected]>

pyproject.toml

@@ -90,6 +90,10 @@ build-dir = "build/{wheel_tag}"
 # Explicitly set the package directory
 wheel.packages = ["src/mqt"]
 
+# Only build the Python bindings target
+cmake.targets = ["_core"]
+
+# Only install the Python package component
 install.components = ["mqt-core_Python"]
 
 metadata.version.provider = "scikit_build_core.metadata.setuptools_scm"