Require call target for multi-contract tests

[erak]

Part of #16394.

Description

Currently, the SolidityExecutionFramework relies on the last compiled contract the CompilerStack knows of. With #16394, we will use the compilers' standard JSON output, which only exposes the compilation order via the AST. Since exporting and parsing the AST JSON output for every test is very expensive, we aim to remove this cost by requiring explicit definition of the contract under test (the contract that is the target of function calls) for tests that define more than one contract.

This means that all semantic tests that define more than one contract must now define which contract should be called. This is done by either specifying the contract programmatically in an end-to-end test or by setting the targetContract in a semantic test file.

For tests that only define one contract, this one will be called and specifying the target contract is not required.

AI Disclosure

• assisted with adding the targetContract setting to all multi-contract tests