Verify and potentially increase test coverage for inheritance and function calls.

We didn't have a single test case that failed on https://github.com/ethereum/solidity/issues/8434 - I added two measly test cases in https://github.com/ethereum/solidity/pull/8436, but that's probably far from enough and I'm afraid this could only be the tip of the iceberg wrt test coverage in this area, so we should check this and potentially add a lot more tests for function calls in general and especially in the presence of various inheritance scenarios.

Review issue 8434 and the two test cases added in pull request 8436 first. Search the repository's existing inheritance and function-call tests, then identify missing combinations and add coverage for the relevant scenarios; done means the regression is covered and broader inheritance/function-call cases are tested.

Written by the indexing model from the issue text.