* unpaired surrogate escape sequences

Fix #1794

$262.agent.MAX_TIME_EPSILON was intended to be used for callers like `Atomics.wait(typedArray, indexNumber, valueNumber, timeoutNumber)` where all parameters with the `Number` suffix denote values which are already Number values. It should not be used for `Atomics.wait(typedArray, indexObject, valueObject, timeoutObject)` where all parameters with the `Object` suffix denote values which are Object values, because in that case we'd require that `ToNumber(objectValue)` (potentially invoked multiple times) completes in less than 100 milliseconds (the default value for MAX_TIME_EPSILON).

Also removes $262.agent.MAX_TIME_EPSILON because it is now no longer used.

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.

Follow up to https://github.com/tc39/test262/pull/1643

All other Proxy tests use the syntax `attr: function() {...}` for
defining traps, ownKeys was unique in using the shorthand syntax. Change
to longhand syntax for back-compat for partial implementations.

Proxy/deleteProperty/boolean-trap-result-boolean-true.js was missing a
feature flag for the Reflect library.

https://github.com/mathiasbynens/unicode-property-escapes-tests/commit/62cbe2f1cb8d5c5ec3841242316b0014a3c82e64