Refactor AST parsing testing

[montyly]

This PR refactor the AST parsing tests:

• We will now have a list of tests, rather than iterating over the tests/ast_parsing directory. We will also stop relying on the filename to know the solc version. This will allow us more fine-grained control over the tests, and ease adding new tests.
• The tests will now install automatically the missing solc version using solc-select
• The tests will not run on new solc version until we update them - this will prevent the CI from failing on every new solc version