Only this test relied on $ERROR throwing a catchable Test262Error.

This change allows test environments to provide their on $ERROR function for better error reporting.

 fix typos in class field templates

Ref https://github.com/tc39/test262/commit/f1602088e6f1277d89548dfacf46dbaa0fb98154#commitcomment-25237057

classfields: eval early errors

BigInt: Add test for BigInt.prototype[Symbol.toStringTag]

Missing generators flags

BigInt64Array/BigUint64Array

BigInt bitshift operators

RegExp property escapes: test Extended_Pictographic

CONTRIBUTING.md: More detail about "features"

typeof fixups

tools/lint: install  PyYAML if not available

BigInt bitwise and, or, xor

DataView.prototype.getBigInt64 tests

Tests the fix for https://github.com/tc39/proposal-bigint/issues/92

CONTRIBUTING.md Fix mistake in test generation section

BigInt: BigInt .toString() returns only decimal digits, does not include BigIntLiteralSuffix

Modify $262.uncallableAndIsHTMLDDA() to an optional $262.IsHTMLDDA (whose use must be guarded by a feature of the same name), and narrowly/correctly prescribe its requirements consistent with `document.all`'s behavior in HTML. 

More class fields test of early errors