Allow cookies with spaces in the name (dotnet/corefx#36566)

Allow cookies with spaces in the name (dotnet/corefx#36566)

* Allow cookies with spaces in the name

* Apply suggestions from code review

Co-Authored-By: PaitoAnderson <pj.paito@gmail.com>
* Added supporting HttpClient functional cookie test

* Updated UWP cookie class and added additional tests

* Prevent cookies with spaces at the start or end

* Forgot UWP

* Fix could allocate on trim

Co-Authored-By: Ben Adams <thundercat@illyriad.co.uk>
* Better cookie space start/end check

Co-Authored-By: Ben Adams <thundercat@illyriad.co.uk>
* Bring checks into line

Co-Authored-By: Ben Adams <thundercat@illyriad.co.uk>
* Skip test on .net framework

* Skip additional tests on .net framework

* Fix typo

Commit migrated from https://github.com/dotnet/corefx/commit/8a22438a1af870cdd04eaf798b155b8a1ab04cb4