Add tests for Annex B "function in block" semantics (procedurally generated)

Add tests for Lexical Environment management

Update testTypedArrayConversions to require byteConversionValues

Add tests for Annex B extns to Date.prototype

- Add tests for abrupt completion handling from ToString operations
- Add tests for method property descriptors
- Remove redundant assertion

Add tests for the spread operator (procedurally generated)

In order to increase the clarity of generated output, select a name for
the test case variable that is not also used by a test template.

Because implementations are free to select any valid NaN value during
GetValueFromBuffer, tests concerning semantics for consistent NaN value
encoding cannot rely on values returned from that abstract operation.

Update the test for `%TypedArray%.prototype.map` to set the same NaN
values via `map` as set in the "control" array.

Extend tests for the `escape` and `unescape` built-ins to assert their
behavior. Rely on the latest ECMAScript draft, which specifies that
`escape` returns hexadecimal codes in upper case.