Additionally removed the `arrow-function` feature for
test/language/eval-code/direct/new.target-fn.js as it is not testing
arrow-functions, but they are mentioned in the preamble.

Early errors may result from parsing the source text of a test file, but
they may also result from parsing some other source text as referenced
through the ES2015 module syntax. The latter form of early error is not
necessarily detectable by ECMAScript parsers, however. Because of this,
the label "early" is not sufficiently precise for all Test262 consumers
to correctly interpret all tests.

Update the "phase" name of "early" to "parse" for all those negative
tests that describe errors resulting from parsing of the file's source
text directly. A forthcoming commit will update the remaining tests to
use a "phase" name that is more specific to module resolution.

This pattern makes expectations more explicit by making test files more
literal.

This re-factors some existing Sputnik tests to be more targeted and to use a
pattern that can be generalized to other forms. We could test these all day,
but I've limited myself to forms introduced in ES2015, specifically
YieldExpression and new.target. Note that SpiderMonkey incorrectly throws a
SyntaxError for these.
I thoughtlessly wrote ReferenceError tests for yield = 1 until I realized
that such productions are not actually recognized by the grammar, so the early
errors do not apply. Instead, I've added a negative syntax test for that case.

* Refactor test for valid cover

* Add tests for ValidSimpleAssignmentTarget

Ensure that constructs introduced in ES2015 are disallowed as assignment
targets, with or without a "cover" grammar.

* Add test for grammar precedence of YieldExpression