Adds fix for issue7262 and a test of it

Created by: spacether

We have an open issue where an allOf composed schema with an inline definition makes the openapi codegen throw an exception. This PR updates our code to skip over those inline schemas So now the exception is not thrown Fixes https://github.com/OpenAPITools/openapi-generator/issues/7262

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Core Team: @wing328 (2015/07) @jimschubert (2016/05) @cbornet (2016/05) @ackintosh (2018/02) @jmini (2018/04) @etherealjoy (2019/06) @spacether (2020/05)