Format negative years in Date string methods

[rogeralsing]

Context: Test262 failures for Date.prototype.toString/toDateString/toUTCString with negative years.

Fixes:

• Add manual formatting helpers that compute year/month/day/weekday/time from ECMAScript time values and format signed years with at least four digits.
• Use manual formatters for out-of-range years in toString/toDateString/toUTCString.

Tests:

• dotnet test tests/Asynkron.JsEngine.Tests.Test262 -c Release --settings tests/Asynkron.JsEngine.Tests.Test262/BuiltInsTests.runsettings --filter "Name=Date_prototype_toDateString|Name=Date_prototype_toString|Name=Date_prototype_toUTCString"

[rogeralsing]

Pushed fix in commit 7a8278c.

Summary:

• Manual formatting for negative/out-of-range years in toString/toDateString/toUTCString.

Tests:

• dotnet test tests/Asynkron.JsEngine.Tests.Test262 -c Release --settings tests/Asynkron.JsEngine.Tests.Test262/BuiltInsTests.runsettings --filter "Name=Date_prototype_toDateString|Name=Date_prototype_toString|Name=Date_prototype_toUTCString"