Add LinkML schema parser utility and corresponding unit test

[khanahmedm]

This PR introduces the new linkml_parser.py module for loading and converting LinkML schemas into Spark-compatible column definitions. It also includes a dedicated unit test suite to validate schema loading, type mapping, and remote/local path handling. No other ingestion logic is modified in this PR.

The full solution is available here in feature/full-solution branch.

[ialarmedalien]

I would advise against adding the linkml parser to the repo now, for the following reasons:

1. it isn’t as fully featured as the one I’m using for the cdm-schema (https://github.com/kbase/cdm-schema/blob/main/linkml_to_pyspark.py)
2. we really want the output — i.e. the pyspark schema (e.g. https://github.com/kbase/cdm-schema/blob/main/src/cdm_schema/kbase_cdm_pyspark.py)
3. the linkml parser would be better as a community-maintained resource in the linkml repo (means others can update/maintain it as it will be in a central location with other linkml converters)

I think it would be more useful to have an importer for pyspark schemas / python modules like the one linked in point 2.