Consolidate tests

[nikodemus]

Goal is to have foo/test.foo run on both host and target, both interpreted and compiled on target.

• TestInteger#testPrintBase: broken on target #849
• Object#== broken on target evaluator #851
• get rid of test_foolang
• get rid of test_transpiler
• combine test.foo and self_test.foo (conditionalize non-host tests explicitly?)