refactor: drop the need to use importlib

[12rambau]

To reach the file system you are using importlib.resources which is basically reading the file tree that exists within the wheel. I was trying to restore functionalities of ee_extra in geetools and I got many failures related to this mechanism (https://github.com/gee-community/geetools/actions/runs/16901688812/job/47882812551?pr=467)

geetools/ee_image.py:1041: in preprocess
    return ee_extra.QA.pipelines.preprocess(self._obj, **kwargs)
.nox/ci-test/lib/python3.9/site-packages/ee_extra/QA/pipelines.py:37: in preprocess
    x = maskClouds(x, **kwargs)
.nox/ci-test/lib/python3.9/site-packages/ee_extra/QA/clouds.py:341: in maskClouds
    platformDict = _get_platform_STAC(x)
.nox/ci-test/lib/python3.9/site-packages/ee_extra/STAC/utils.py:21: in _get_platform_STAC
    eeDict = _load_JSON()
.nox/ci-test/lib/python3.9/site-packages/ee_extra/utils.py:19: in _load_JSON
    data_file = files("ee_extra.data") / x
/opt/hostedtoolcache/Python/3.9.23/x64/lib/python3.9/importlib/resources.py:147: in files
    return _common.from_package(_get_package(package))
/opt/hostedtoolcache/Python/3.9.23/x64/lib/python3.9/importlib/_common.py:14: in from_package
    return fallback_resources(package.__spec__)
/opt/hostedtoolcache/Python/3.9.23/x64/lib/python3.9/importlib/_common.py:18: in fallback_resources
    package_directory = pathlib.Path(spec.origin).parent
/opt/hostedtoolcache/Python/3.9.23/x64/lib/python3.9/pathlib.py:1000: in __new__
    self = cls._from_parts(args, init=False)
/opt/hostedtoolcache/Python/3.9.23/x64/lib/python3.9/pathlib.py:625: in _from_parts
    drv, root, parts = self._parse_args(args)

TypeError: expected str, bytes or os.PathLike object, not NoneType

I don't really know how to debug this and I personnaly think relying on importlib is an overkill. In this PR I propose a method that only rely on pathlib to find all the files we need to perform the computation. It will work just as pckg_resources as long as you are not editing the pakg file names when building the wheel (whic is not the case now)