test/matchers: put haveJsOutput into its own file.
test/matchers: rename evaluates_to.js => has_string_output.js.
test/matchers: recursively convert r5js.JsonValues during matching.
test: bring a few more JsInterop tests back online.
submodule+test: bump tdd and remove impls of tdd.matchers.Matcher#getSuccessMessage.
test: remove old test-specific web worker setup.