*because of tons of changes, I will supply the changelists in the email because it was too large for this checkin*
[CL 2483008 by Todd Eckert in Main branch]
UE-9790 - Fixing widget reflector to not crash on UMG widgets that have no associated blueprint asset.
#lockdown Matt.Kuhlenschmidt
[CL 2449857 by Matthew Griffin in Main branch]
* Removed SWidget:: GetCreatedInFile, GetCreatedInFileFName, GetCreatedInLineNumber.
* Added GetCreatedInLocation() -> FName as a non-redundant replacement, updated all code usages.
* This shrinks SWidget size by 16 bytes and reduces ambiguity on which ones to use.
* Implemented ToString() in terms of GetReadableLocation().
#codereview:max.preussner
[CL 2430545 by Wes Hunt in Main branch]
* See SlateStats.h for details on the new system, which allows for full hierarchical profiling with limited overhead.
* Moved SWidget::GetVisibility() out of line so we can instrument it without a full recompile.
* Widget debug info now uses FName to store the line number of the file. Keeps it in one place and the new stats system can utilize it as an FName.
* Exposed SWidget CreatedInFile debug info as an FName so new stats system can use it.
* FSlateVertex no longer uses FVector4, which is an aligned struct. Switched to float[4] instead. Goes from 48 to 36 bytes.
#codereview:nick.atamas,matt.kuhlenschmidt
[CL 2417281 by Wes Hunt in Main branch]
Moved the existing atlas visualizer out of the Slate RHI renderer and instead made the resource manager for each renderer implement the ISlateAtlasProvider interface to provide information about its current texture atlases. FSlateFontCache implements ISlateAtlasProvider for the font atlas viewer.
Improved the atlas visualizer and added support for zooming and panning of the atlas pages. This helps greatly when viewing font atlases as they can be as large as 2048x2048.
#codereview Matt.Kuhlenschmidt
[CL 2371483 by Jamie Dale in Main branch]
Text : FNumberFormattingOptions now provides method-chainable settings for easily creating a static const instance.
#codereview Justin.Sargent,Jamie.Dale
[CL 2350380 by Nick Atamas in Main branch]
