Rename and consolidate tests in future-reserved-words directory

test/language/future-reserved-words/interface-strict.js

test/language/future-reserved-words/interface.js

test/language/future-reserved-words/let-strict-escaped.js

test/language/future-reserved-words/let-strict.js

test/language/future-reserved-words/long.js

test/language/future-reserved-words/native.js

.../language/future-reserved-words/package-strict-escaped.js

test/language/future-reserved-words/package-strict.js

test/language/future-reserved-words/package.js

.../language/future-reserved-words/private-strict-escaped.js

test/language/future-reserved-words/private-strict.js

test/language/future-reserved-words/private.js

...anguage/future-reserved-words/protected-strict-escaped.js

test/language/future-reserved-words/protected-strict.js

test/language/future-reserved-words/protected.js

test/language/future-reserved-words/public-strict-escaped.js

test/language/future-reserved-words/public-strict.js

test/language/future-reserved-words/public.js

test/language/future-reserved-words/short.js

test/language/future-reserved-words/static-strict-escaped.js