Fixed crd_to_kcl.sh to work with latest kcl import structure

[kukacz]

This change aligns the crd_to_kcl.sh script to work correctly after recent changes in kcl import and
adds a small improvement in source package version handling:

• Part handling the API version detection and organizing imported files into appropriate subdirectories was removed as this is now directly handled by kcl import.
• Optional command line argument "version-tag" was added, allowing to specify version tag used by the source repository. This version is automatically added into kcl.mod as version of KCL package.
• The script drops incoming schema versions identified as "unknown", since those can't be reliably executed. Kindly verify this proposal during review process.

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[Peefy]

Thank you!