Upgrade schemapack to 2.0.0-alpha3 in 'schemapack' branch

[lkuchenb]

This patch migrates the schemapack branch to schemapack 2.0.0-a3. The previously migrated transformations have been migrated to the current schemapack 2.x standard.

Notable changes

• The multiplicity parameter of the infer relations transformation has been removed. I believe the multiplicity and mandatoriness :-) can be inferred as implemented here. However, maybe these should go to the path submodule (which in turn should move up the module hierarchy if we are going to re-use it in other transformations as planned)?
• I've added a placeholder dev_launcher script to re-enable Dockerfile updates through the template update mechanism.

[coveralls]

Pull Request Test Coverage Report for Build 9080458434

Details

• 63 of 67 (94.03%) changed or added relevant lines in 7 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.2%) to 93.345%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/metldata/builtin_transformations/infer_relations/data_transform.py	7	9	77.78%
src/metldata/builtin_transformations/infer_relations/model_transform.py	41	43	95.35%

Totals
Change from base Build 8848794681:	-0.2%
Covered Lines:	519
Relevant Lines:	556

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💛 - Coveralls

[Cito]

Looks good to me.

When running the tests, I get a deprecation warning from pydantic and another user warning. These should be fixed in another PR.

[lkuchenb]

Thanks @Cito, ready for another round