fix: don't keep reinstalling local pypi archives

[tdejager]

When using a pypi local archive things keep reinstalling.

[workspace]
authors = ["Tim de Jager <tim@prefix.dev>"]
channels = ["https://prefix.dev/conda-forge"]
name = "installation-order"
platforms = ["osx-arm64"]
version = "0.1.0"

[tasks]

[dependencies]
python = "3.13.*"

[pypi-dependencies]
minimal = { path = "./minimal-0.1.0-py2.py3-none-any.whl" }

...
 INFO pixi::install_pypi: 4 of 5 required packages are considered are installed and up-to-date
 INFO pixi::install_pypi: *re-installing* following packages: minimal
 INFO pixi::install_pypi: re-installing 'minimal' because: 'Git archive is a path'
 INFO pixi::install_pypi: Prepared 1 package in 0ms
 INFO pixi::install_pypi: Installed 1 package in 1ms
✔ The default environment has been installed.

The above kept happening. This PR fixes that behavior.

This pull request includes several changes to the src/install_pypi/plan/test/harness.rs, src/install_pypi/plan/test/mod.rs, and src/install_pypi/plan/validation.rs files to improve the handling of PyPI package installations and their validation.

The most important changes are summarized below:

Improvements to PyPI package data handling:

• Renamed the directory function to path in impl PyPIPackageDataBuilder to better reflect its purpose.
• Added a new method add_local_wheel to RequiredPackages for adding local wheel files.

Enhancements to test harness:

• Introduced install_planner_with_lock_dir function to create an InstallPlanner with a specified lock directory. This will help for relative path testing.
• Added fake_wheel function to create a fake wheel file for testing purposes.

Validation improvements:

• Updated error handling in NeedsReinstallError to include a new variant FreshnessError for errors encountered while checking freshness.
• (The fix) Enhanced the need_reinstall function to handle relative paths and check the freshness of URLs more robustly. [1] [2]