Improve allocations in WinForms startup (dotnet/corefx#39275)

Improve allocations in WinForms startup (dotnet/corefx#39275)

* Strip out delegate API calls and use the SetDllImportResolver functionality instead.

* Fix the Unix buidl

* Fix NetFX build, create class for custom resolving

* Fix namespace, tweak comments in project file

* Tweak LibraryResolver per feedback

* Fix  breaks

* Adjust tests for NetFX behavior

* Harvest downlevel packages

* Put back UAP build, respond to feedback on projects and LOGFONT marking

* Remove local

* Tweak FileNotFoundException, guard in PageSettings

* Address feedback

Change LOGFONT round tripping to allow structs

* Fix hintpath. Finish fixing LOGFONT references.

* Address feedback

Commit migrated from https://github.com/dotnet/corefx/commit/b75421a0035bf3a44e1f68447255470d57074dbb