Module semantics: declaration instantiation

[jugglinmike]

Files whose name ends in _.js are not themselves valid Test262 tests
and should not be interpreted as such by test runners.

---

Because the tests in this patch concern declaration instantiation,
care has been taken to avoid asserting binding values following
evaluation. Because a given module's dependencies are evaluated prior to
the module itself, this is only observable in modules which import their
own bindings.

A separate patch dedicated to the evaluation of module code asserts the
behavior of bindings following evaluation.

---

For tests that concern the creation of a module namespace object, this
patch relies on the semantics of the in operator. The in operator
uses the [[HasProperty]] internal method and avoids testing unrelated
semantics concerning binding resolution. Those semantics should be
explicitly asserted with a separate set of tests dedicated to that
purpose.

---

One test case which is notably missing is error resulting from a cycle
due to an import declaration (under the current file naming scheme,
such a test might be named instn-named-err-circular.js). Due to the
recursive nature of ModuleDeclarationInstantiation, it is not
technically possible for a circular request to be found in step 12.c.i.
Cycles rely on at least 2 export declarations, and because these are
resolved before imports, any cycle would trigger failure prior to step
12.c.

---

One aspect of module resolution that makes ordering observable is the
fact that resolution can fail in two distinct ways (i.e. with a
SyntaxError or with a ReferenceError). This patch includes tests that
leverage this detail in order to assert that modules are resolved in the
correct sequence.

However, from the perspective of the ECMA-262 specification, the
ordering of export (e.g. binding) resolution is not observable. This
is due to restrictions on the grammar, where each export is independent.
When export resolution fails, it does so with instances of SyntaxError
alone, precluding the above strategy.

So while ModuleDeclarationInstantiation resolves the exports of the
module's dependencies in the following order:

1. "Indirect" exports, e.g.
   • export { x } from './y.js';
   • export { x as z } from './y.js';
   • import { x } from './y.js'; export { x };
2. "Star" imports
   • import * as ns from './y.js';
3. "Named" (my word) imports
   • import x from './y.js';
   • import { x } from './y.js';
   • import { x as z } from './y.js';

Intentional failures cannot be used to discern resolution ordering.

[goyakin]

@boingoing & @Yongqu, could you take a look?