[FEATURE] Support PEP 440 direct references to source packages

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As documented https://pip.pypa.io/en/stable/cli/pip_install/#examples (point 9), it is possible to define requirements as follows, which this library cannot parse at present:

```
python -m pip install SomeProject@http://my.package.repo/SomeProject-1.2.3-py33-none-any.whl
python -m pip install "SomeProject @ http://my.package.repo/SomeProject-1.2.3-py33-none-any.whl"
python -m pip install SomeProject@http://my.package.repo/1.2.3.tar.gz
```

Validating the above with `pip` `22.0.4` as follows:
```
> python -m pip install "Jake @ https://files.pythonhosted.org/packages/d1/aa/e1be071cde813cafca797678c728b9fa686aa7d72c3e10c512ac7a5599d2/jake-2.0.0-py3-none-any.whl"
...

> pip freeze
...
jake @ https://files.pythonhosted.org/packages/d1/aa/e1be071cde813cafca797678c728b9fa686aa7d72c3e10c512ac7a5599d2/jake-2.0.0-py3-none-any.whl
...
```

This feature should parse the above example to a `Requirement` as follows:
```
{
"line": "jake @ https://files.pythonhosted.org/packages/d1/aa/e1be071cde813cafca797678c728b9fa686aa7d72c3e10c512ac7a5599d2/jake-2.0.0-py3-none-any.whl",
"editable": false,
"local_file": false,
"specifier": false,
"vcs": null,
"revision": null,
"name": "jake",
"uri": "https://files.pythonhosted.org/packages/d1/aa/e1be071cde813cafca797678c728b9fa686aa7d72c3e10c512ac7a5599d2/jake-2.0.0-py3-none-any.whl",
"subdirectory": null,
"path": null,
"hash_name": null,
"hash": null,
"extras": [],
"specs": []
}
```

Start by reproducing the documented PEP 440 direct-reference examples with pip 22.0.4 and trace how the parser currently handles these requirement lines. The work is done when the examples produce a Requirement with the fields and values shown in the issue, including the package name and URI.

Written by the indexing model from the issue text.