* Remove tracerfactory and tracerbuilder
* Remove tracer extensions
* Add Span and Tracer shims. Remove all span code.
* more wrapper apis
* Wrap ActivityEvent
* wrap links
* change tracestate back to keyvalue pair in contxt
* ore tracer fix
* OpenTracing shim
* example change
* remove spancontext
* remove more of the new stuffs
* benchmark fixes
* remove Event class
* TraceState consistent name
* casing fix
* equality fix
* fix test
* test todo
* typo
* rename after accepting shim chanegs from Raj
* remove new from the end of many names.
* benchmark fix
* TraceStateUtils naming
* TraceStateUtilsNew rename to fix build issue at CI.
* renamings