Static fields were broken up from instance fields and demoted to
Stage 2 in the November 2017 TC39 meeting. This patch removes the
test262 tests which test static class fields.

BigInt.parseInt will be removed in
https://github.com/tc39/proposal-bigint/pull/101

This patch removes the associated test262 tests.

The `groups` property must be created unconditionally. https://github.com/tc39/proposal-regexp-named-groups/pull/40

The use of `let` is unnecessary here, particularly in a
file that is needed to run any of the tests, even the ES5 tests.
Removing it allows older engines to run older tests.

Refactor AssignmentExpression tests for parsers

Correct metadata reference in "contributing" docs

Remove some spurious blank lines

Formalize installation procedure

A number of tests for the parsing of the AssignmentExpression production
were expressed using `eval`. This made the tests more complex than
necessary, and also prevented the tests from providing value to
ECMAScript parsers.

Remove the use of `eval` in the relevant tests and instead express the
expectations with literal source text. Remove superfluous "onlyStrict"
restriction from tests by declaring the probe binding prior to
assignment.

A few BigInt tests had a blank line in an inconvenient place which
breaks an old, possibly incorrect YAML parser used by V8's test262
test automation. The best fix is to deploy a new YAML parser, but
in the short term, this patch deletes the blank lines and lets
V8 understand the feature flags below. Related: #1370

Ensure that the linter's Python dependencies are satisfied in the
continuous integration environment.

Note that this is not currently necessary but only because the linter's
dependencies happen to align with those of the test generation tool. The
dependencies of the two tool should be satisfied explicitly in order to
promote isolation.

Split class fields tags